feat: ForceStreamSession 覆盖 field 与 FN-only 标定（T06b）

新增 measurement_requirements，告知调用方 field 模型需要同帧场数据。补充标量、field、FN-only 三类标定与旧 ForceSession 的数值等价测试，以及标定与帧不匹配的情况：field 缺 context 时构造失败，基线帧缺 field 时零点失败，ready 后缺 field 的帧单独标为 invalid_input。与改动前的旧会话基线逐位一致。回归 381 项、lint 通过。

docs/force-stream-session.zh.md

@@ -1,14 +1,18 @@
-# 新力侧会话（T06a）
+# 新力侧会话（T06a/T06b）
 
-本文件是单路 SensorStream 计划 T06a 的 SDK 合同：新的力侧会话直接消费 T05 的
+本文件是单路 SensorStream 计划 T06a/T06b 的 SDK 合同：新的力侧会话直接消费 T05 的
 `ImageMeasurement`（T03 `MeasurementFrame` 头 + 同帧 raw/field），参考版本取帧上的
 `reference_generation`。旧 `ForceSession` 仍为 App 保留到 T09/T10 迁移，本会话不提供
 `process_measurement`、`request_zero_external_reset`、`tracker_reset_seq` 等旧外部复位接口。
 
 ## 接口
 
-- `ForceStreamSession(sensor_family=..., calibration=None, settings=None)`：构造；T06a 支持
+- `ForceStreamSession(sensor_family=..., calibration=None, settings=None)`：构造。T06a 支持
-  无标定与 schema2 标量曲线，`settings` 为 `OutputSettings`（None 用旧默认）。
+  无标定与 schema2 标量曲线；T06b 补充 schema3 field 模型（`hhd_normal_l1_field/1`，需要
+  `context` 与同帧 field）和 FN-only 全局增益模型（`outputs=["fn"]`）；`settings` 为
+  `OutputSettings`（None 用旧默认）。
+- `measurement_requirements`：`(want_field, want_contact)`，告诉 T05 调用方是否需要把
+  `field` include 进 `ImageMeasurement`（field 模型为 `(True, False)`，标量/FN-only 为 `(False, False)`）。
 - `request_zero(reference_id=..., declared_unloaded=True, expected_reference_generation=版本, max_gap_s=None, max_window_s=None)`：
   为指定参考版本确认无载归零；可选窗口上限。
 - `process(measurement) -> ForceStreamOutput`：消费一个 T05 `ImageMeasurement`，返回逐帧结果
@@ -34,11 +38,15 @@
   `reference_generation`；`quality` 为 `ok` / `uncalibrated` / `zero_pending` / `duplicate` /
   `late` / `session_changed` / `version_changed` / `window_failed` / `invalid`。
   迟到、无效和带质量标记的结果不会被丢弃；拒绝帧仍保留 raw 特征。
-- **数值等价与滤波。** T06a 的零点/标定换算/读数滤波复用已发布算法；同一输入、无复位、
+- **数值等价与滤波。** 零点/标定换算/读数滤波复用已发布算法；同一输入、无复位、同一标定时
-  同一标定时与旧 `ForceSession` 逐帧相等（测试覆盖标量曲线、无标定、median+lowpass 滤波器）。
+  与旧 `ForceSession` 逐帧相等（T06a 覆盖标量曲线、无标定、median+lowpass 滤波器；T06b 覆盖
+  `context` 与同帧 field）和 FN-only 全局增益模型（`outputs=["fn"]`）；`settings` 为
   固定设计帧率与显式滤波切换属于 T07，不在本会话实现。
+- **三类标定与不匹配。** 标量曲线、field、FN-only 各有有效测试；无标定会话保持 raw 与
+  `uncalibrated` 状态；field 模型缺 `context` 时构造报 `CalibrationError`，基线帧缺 field 或
+  模型拒绝帧时零点失败并给出 `invalid_input`/原因；FN-only 的 FX/FY 永远保持 NaN +
+  `uncalibrated`，不冒充三轴标定。
 - **线程与只读。** 一个实例只属于一个力侧线程；输入数组只读，输出只含标量/状态/不可变进度。
-  T06b 在本合同上补充 field 模型、FN-only 全局增益模型与三类标定的完整等价测试。
 
 ## 示例
 
@@ -64,8 +72,8 @@ assert row.zero.phase in ("resetting", "collecting")
 
 ## 后续
 
-T06b：field（`hhd_normal_l1_field/1`）与 FN-only（schema3 `outputs=["fn"]`）标定、标定不匹配、
+T06b 已交付标量/field/FN-only 三类标定与旧 ForceSession 的完整数值等价；spatial_gain/接触
-field 加权基线与标量力域基线的分离，以及对照旧 ForceSession 的完整五场景数值等价。
+映射模型不在 T06b 验收范围，需要时另立任务。
 T07 才改变输出滤波的帧率与切换语义；T09/T10 迁移 App 后删除旧 `ForceSession`。
 另一项后续任务：删除旧 `ForceSession` 之前，先把零点、标定、读数引擎从旧类中抽出来，
 避免新会话依赖待删除的类型（T06b 或 T09 之前）。

src/orisys/force_stream_session.py

@@ -194,6 +194,17 @@ class ForceStreamSession:
     def last_output(self) -> ForceStreamOutput | None:
         return self._last_output
 
+    @property
+    def measurement_requirements(self) -> tuple[bool, bool]:
+        """``(want_field, want_contact)`` the installed calibration model asks for.
+
+        A field model (``hhd_normal_l1_field/1``) asks for the same-frame field, so
+        a T05 caller must include ``field`` in the ``ImageMeasurement``; a
+        scalar/FN-only model asks for neither. The engine's answer is reused
+        instead of a second interpretation of the model.
+        """
+        return self._engine.measurement_requirements
+
     @property
     def reference_generation(self) -> int | None:
         """The reference generation this session currently accepts frames for."""

tests/test_force_stream_session.py

@@ -15,6 +15,7 @@ import importlib.util
 from pathlib import Path
 
 import numpy as np
+import pytest
 
 from orisys.force_stream_session import ForceStreamOutput, ForceStreamSession
 from orisys.image_pipeline import ImageMeasurement
@@ -44,6 +45,8 @@ def _measurement(
     sensor_id: str = "TEST-1",
     capture_time_ns: int | None = None,
     source_frame_id: int | None = None,
+    field: dict | None = None,
+    valid_mask: np.ndarray | None = None,
 ) -> ImageMeasurement:
     stamp = FrameStamp(
         sensor_id=sensor_id,
@@ -61,7 +64,14 @@ def _measurement(
         source_dt_s=None if frame_id == 1 else FRAME_NS / 1e9,
         reference_generation=version,
     )
-    return ImageMeasurement(frame=frame, force_raw=raw, torque=0.0, flow=None)
+    return ImageMeasurement(
+        frame=frame,
+        force_raw=raw,
+        torque=0.0,
+        flow=None,
+        field=field,
+        valid_mask=valid_mask,
+    )
 
 
 def _raw_for(frame_id: int) -> tuple[float, float, float]:
@@ -419,3 +429,243 @@ def test_version_change_branch_frame_is_registered_for_duplicate_detection() ->
     assert repeat.duplicate is True
     assert repeat.quality == "duplicate"
     assert new.zero == after_change, "duplicate must not be processed again"
+
+
+# ------------------------------------------- T06b: field and FN-only calibration
+def _field_payload_for(frame_id: int):
+    return helpers._field_payload(0.5 + 0.05 * frame_id, 0.5)
+
+
+def _field_models(tmp_path):
+    document, context = helpers._field_document(tmp_path)
+    old_model = helpers.parse_model(document, tmp_path / "field-calibration-old.json")
+    new_model = helpers.parse_model(document, tmp_path / "field-calibration-new.json")
+    return old_model, new_model, context
+
+
+def _field_measurement(frame_id: int, *, include_field: bool = True, mask=None):
+    return _measurement(
+        frame_id,
+        (0.0, 0.0, 0.0),
+        field=_field_payload_for(frame_id) if include_field else None,
+        valid_mask=np.ones((4, 4), dtype=bool) if mask is None else mask,
+    )
+
+
+def _field_old(tmp_path):
+    old_model, new_model, context = _field_models(tmp_path)
+    source = helpers.FakeMeasurementSource(
+        lambda frame_id: (0.0, 0.0, 0.0),
+        field_for=_field_payload_for,
+        output_mask=np.ones((4, 4), dtype=bool),
+    )
+    session = helpers.ForceSession(
+        source=source,
+        sensor_family="finger",
+        context=context,
+        calibration=old_model,
+        settings=helpers.legacy_settings(),
+    )
+    return session, source, new_model, context
+
+
+def _compare_field_with_old(tmp_path) -> None:
+    old, source, new_model, context = _field_old(tmp_path)
+    new = ForceStreamSession(
+        sensor_family="finger",
+        context=context,
+        calibration=new_model,
+        settings=helpers.legacy_settings(),
+    )
+    assert new.measurement_requirements == (True, False)
+    old.request_zero(reference_id="field-ref", declared_unloaded=True)
+    new.request_zero(
+        reference_id="field-ref",
+        declared_unloaded=True,
+        expected_reference_generation=0,
+    )
+    old_raw, old_newton, old_status = [], [], []
+    new_raw, new_newton, new_status = [], [], []
+    for frame_id in range(1, 41):
+        old_out = helpers.process(old, source, frame_id)
+        new_out = new.process(_field_measurement(frame_id))
+        old_raw.append(np.asarray(old_out.raw))
+        old_newton.append(np.asarray(old_out.newton))
+        old_status.append(list(old_out.measurement.newton_status))
+        new_raw.append(np.asarray(new_out.raw))
+        new_newton.append(np.asarray(new_out.newton))
+        new_status.append(list(new_out.newton_status))
+    assert np.array_equal(np.stack(old_raw), np.stack(new_raw), equal_nan=True)
+    assert np.array_equal(np.stack(old_newton), np.stack(new_newton), equal_nan=True)
+    assert old_status == new_status
+    assert new.zero.phase == "ready"
+    # The field model outputs FN only; shear axes stay explicitly unavailable.
+    assert np.isfinite(new_newton[-1][0])
+    assert np.isnan(new_newton[-1][1]) and np.isnan(new_newton[-1][2])
+    assert new_status[-1][1:] == ["uncalibrated", "uncalibrated"]
+
+
+def _fn_only_models():
+    context = helpers.build_context(
+        {
+            "camera": {"resolution_stitch": [4, 4]},
+            "tracker": {"dis_mode": 1, "hhd_downsample": 1},
+        }
+    )
+    document = helpers._global_gain_document(context, gains={"fn": 0.01})
+    old_model = helpers.parse_model(document)
+    new_model = helpers.parse_model(document)
+    return old_model, new_model, context
+
+
+def _fn_raw(frame_id: int) -> tuple[float, float, float]:
+    return (100.0 + frame_id, 7.0, -7.0)
+
+
+def _compare_fn_only_with_old() -> None:
+    old_model, new_model, context = _fn_only_models()
+    source = helpers.FakeMeasurementSource(_fn_raw)
+    old = helpers.ForceSession(
+        source=source,
+        sensor_family="box",
+        context=context,
+        calibration=old_model,
+        settings=helpers.legacy_settings(),
+    )
+    new = ForceStreamSession(
+        sensor_family="box",
+        context=context,
+        calibration=new_model,
+        settings=helpers.legacy_settings(),
+    )
+    assert new.measurement_requirements == (False, False)
+    old.request_zero(reference_id="fn-ref", declared_unloaded=True)
+    new.request_zero(
+        reference_id="fn-ref",
+        declared_unloaded=True,
+        expected_reference_generation=0,
+    )
+    old_raw, old_newton, old_status = [], [], []
+    new_raw, new_newton, new_status = [], [], []
+    for frame_id in range(1, 41):
+        old_out = helpers.process(old, source, frame_id)
+        new_out = new.process(_measurement(frame_id, _fn_raw(frame_id)))
+        old_raw.append(np.asarray(old_out.raw))
+        old_newton.append(np.asarray(old_out.newton))
+        old_status.append(list(old_out.measurement.newton_status))
+        new_raw.append(np.asarray(new_out.raw))
+        new_newton.append(np.asarray(new_out.newton))
+        new_status.append(list(new_out.newton_status))
+    assert np.array_equal(np.stack(old_raw), np.stack(new_raw), equal_nan=True)
+    assert np.array_equal(np.stack(old_newton), np.stack(new_newton), equal_nan=True)
+    assert old_status == new_status
+    assert new.zero.phase == "ready"
+    assert np.isfinite(new_newton[-1][0])
+    assert np.isnan(new_newton[-1][1]) and np.isnan(new_newton[-1][2])
+    assert new_status[-1][1:] == ["uncalibrated", "uncalibrated"]
+
+
+def test_field_model_matches_old_session_on_this_platform(tmp_path) -> None:
+    _compare_field_with_old(tmp_path)
+
+
+def test_fn_only_model_matches_old_session_on_this_platform() -> None:
+    _compare_fn_only_with_old()
+
+
+def test_three_calibration_types_match_the_old_session_on_this_platform(
+    tmp_path,
+) -> None:
+    # Same interpreter/platform for both chains: no cross-OS golden comparison.
+    _compare_with_old(helpers.box_cal())  # schema2 scalar curves
+    _compare_field_with_old(tmp_path)  # schema3 field model (FN-only)
+    _compare_fn_only_with_old()  # schema3 global gain (FN-only)
+
+
+def test_field_model_requires_context_and_field_frame(tmp_path) -> None:
+    from orisys.calibration import CalibrationError
+
+    old_model, new_model, context = _field_models(tmp_path)
+    with pytest.raises(CalibrationError, match="pipeline context"):
+        ForceStreamSession(sensor_family="finger", calibration=old_model)
+
+    session = ForceStreamSession(
+        sensor_family="finger",
+        context=context,
+        calibration=new_model,
+        settings=helpers.legacy_settings(),
+    )
+    session.request_zero(
+        reference_id="field-ref",
+        declared_unloaded=True,
+        expected_reference_generation=0,
+    )
+    missing = session.process(_field_measurement(1, include_field=False))
+    assert missing.zero.phase == "failed"
+    assert "invalid_input" in missing.zero.failure_reason
+    assert all(np.isnan(value) for value in missing.newton)
+    assert missing.newton_status[0] == "invalid_input"
+
+
+def test_field_model_uncalibrated_session_stays_explicit(tmp_path) -> None:
+    _, _, context = _field_models(tmp_path)
+    new = ForceStreamSession(
+        sensor_family="finger",
+        context=context,
+        calibration=None,
+        settings=helpers.legacy_settings(),
+    )
+    new.request_zero(
+        reference_id="field-raw",
+        declared_unloaded=True,
+        expected_reference_generation=0,
+    )
+    rows = [_field_measurement(frame_id) for frame_id in range(1, 32)]
+    results = [new.process(row) for row in rows]
+    assert results[-1].zero.phase == "ready"
+    assert all(np.isnan(value) for value in results[-1].newton)
+    assert set(results[-1].newton_status) == {"uncalibrated"}
+    assert results[-1].quality == "uncalibrated"
+
+
+def test_fn_only_model_requires_context_and_rejects_invalid_frames() -> None:
+    from orisys.calibration import CalibrationError
+
+    old_model, new_model, context = _fn_only_models()
+    with pytest.raises(CalibrationError, match="pipeline context"):
+        ForceStreamSession(sensor_family="box", calibration=old_model)
+
+    new = ForceStreamSession(
+        sensor_family="box",
+        context=context,
+        calibration=new_model,
+        settings=helpers.legacy_settings(),
+    )
+    new.request_zero(
+        reference_id="fn-ref", declared_unloaded=True, expected_reference_generation=0
+    )
+    invalid = new.process(_measurement(1, (float("nan"), 7.0, -7.0)))
+    assert invalid.zero.phase == "failed"
+    assert "invalid input frame" in invalid.zero.failure_reason
+    assert all(np.isnan(value) for value in invalid.newton)
+
+
+def test_fn_only_model_uncalibrated_session_stays_explicit() -> None:
+    _, _, context = _fn_only_models()
+    new = ForceStreamSession(
+        sensor_family="box",
+        context=context,
+        calibration=None,
+        settings=helpers.legacy_settings(),
+    )
+    new.request_zero(
+        reference_id="fn-raw", declared_unloaded=True, expected_reference_generation=0
+    )
+    results = [
+        new.process(_measurement(frame_id, _fn_raw(frame_id)))
+        for frame_id in range(1, 32)
+    ]
+    assert results[-1].zero.phase == "ready"
+    assert all(np.isnan(value) for value in results[-1].newton)
+    assert set(results[-1].newton_status) == {"uncalibrated"}
+    assert results[-1].quality == "uncalibrated"