fix(studio-3d): 字段级来源与失效状态 —— 旧光流/算法失败不再冒充实时测量

- What:
  1. **采集侧声明每个派生数组的归属**（`acquisition/models.py`）：`SdkPacket` 新增
     `flow_valid/flow_frame_id/depth_valid/depth_frame_id/forces_valid`（`None` = 未声明）。两个真实
     生产者都填写：`finger_worker`/`sdk_worker` 逐帧记录"该数组实际算出来的 frame_id"，链失败时
     `*_valid=False` 并把上一次成功帧号带出来。光流与形变链分开判定（力读取失败不等于光流失败），
     但算法链失败时本帧的一切派生量都不可声明。
  2. **adapter 按声明收数据**（`scene3d/adapters.py`）：`_field_validity()` 三态——未声明 → 拒绝并报
     `field_unverified`（没声明就不算数）；声明为假 → `field_stale`（把 `invalid_reason` 带进诊断）；
    声明帧号不是本帧 → `field_stale`（两个帧号都写进 details）。`_intersect_device_mask` 换成
     `_device_mask`：设备 mask 形状不符**拒绝该帧**（`field_domain_mismatch`，两个形状都写进诊断），
     既不拉伸也不静默忽略。发布的帧带 `computed_frame_id`，身份一路带到显示侧。
  3. **契约**（`scene3d/contracts.py`）：`SceneState` 加 `"stale"`；诊断码加 `field_stale`/`field_unverified`
     （warning）；`SurfaceFieldFrame.computed_frame_id` 与 `RenderFrame.computed_frame_id`（由 composer
     原样透传）；`validate_surface_frame` 校验帧号非负且不晚于所属帧。新增 locale：
     `scene3d.state_stale`（中英各一条）。
  4. **协调器不再"边失败边报 live"**（`scene3d/coordinator.py`）：新增 `_stale_since` 宽限状态机与
     `note_field_failure()`——字段被拒、帧被判 invalid、compose 抛错、或合成结果的 `computed_frame_id`
     落后于本帧，都立即把状态改为 `stale` 并保留最后一帧；宽限（`stale_grace_s`，默认 1.0 s）到期后
     回参考模型并转 `no_data`；收到好帧即回 `live` 并清掉宽限。顺带修掉"等待首帧时每个 tick 都把参考
     模型重新 present 一次"（`_rest_presented`，16 ms 一次的无谓上传）。
  5. **诊断真正到达界面**（`scene3d/view.py`）：`submit_packet()` 在 adapter 拒绝时把
     `adapter.last_diagnostic` 交给 `note_field_failure()`；`tick()` 把协调器诊断的变化经已有
     `diagnosticRaised` 冒泡（协调器自身仍然零 Qt 依赖）。新增 `_snapshot_diagnostic()` 与 `_adapter`
     引用（后续"按能力禁用控件"也要问它）。
- Why: 审查报告 P1/R2：`FingerFrameAdapter.snapshot()` 从不读 `valid`/`stale_forces`/`invalid_reason`，
  只看到有限的 `flow` 就当作新数据上色（复现：`valid=False, stale_forces=True` + 有限 flow → 仍有有效
  着色点、diagnostic=None）；compose 抛错只写 `last_diagnostic`，画面与 `state` 保持不变；
  `snapshot()` 返回 None 时诊断无人读取；mask 域不符时静默忽略会扩大可信范围。力读数失败不该机械地
  判死三维，但算法失败也不能因为旧数组是有限值就当成新数据——所以按**字段级来源**处理，并让失效有
  明确的、可见的状态而不是继续保持 live。
- Verification:
  · `test_scene3d_adapters.py` 23 通过（+6 新增）：stale flow 被拒且带原因、未声明 flow → `field_unverified`、
  帧号不符 → `field_stale`（details 两个帧号）、新帧记录 `computed_frame_id`、box 侧"形变链失败仍用光流"、
  box 全部字段不可声明时拒绝；mask 域不符由"被忽略"改为"拒绝该帧"（原断言已改）。
  · `test_scene3d_coordinator.py` 30 通过（+6 新增）：落后帧号的合成结果永不上屏且状态 stale、
  字段被拒 → 宽限内保留画面/宽限后回参考模型/好帧回 live、compose 抛错不再保持 live、invalid 帧也计入
  宽限。
  · `test_scene3d_view.py`（+3 新增，offscreen 可跑）：adapter 拒绝 → 协调器 stale 且诊断经
  `diagnosticRaised` 回到面板、`scene3d.state_stale` 不是裸键；未声明字段 → `field_unverified`；
  新鲜字段照常上屏回到 live。
  · 全量：apps/studio 228 项 0 失败 14 跳过；shared 301 项 0 失败 1 跳过（`--junitxml` 计数）。
- Not in this change: `docs/architecture/studio-3d-contracts.pyi` 与新契约的同步放在阶段 6 的文档提交里
  一起做（本阶段契约改动较多，避免每提交改一次文档）；设备几何身份（R3）、资产加载请求号（R7）、
  二维后端统一、限速与真实统计均未动；真机上"链失败时 VRAW 是否也过期"这一条仍需实测（若证明链失败
  不影响 VRAW，`flow_valid` 放宽为只看读取结果是一行改动，已写进计划的风险项）。

apps/studio/tests/test_scene3d_view.py

@@ -22,6 +22,7 @@ from __future__ import annotations
 
 import itertools
 import shutil
+import time
 from dataclasses import replace
 from pathlib import Path
 
@@ -610,6 +611,89 @@ def test_a_finger_scene_uses_the_finger_adapter(tmp_path, write_poc, qt_app):
         view.close()
 
 
+# ------------------------------------------- stage 6: a field that is not this frame's
+def _stale_scene_view(qt_app):
+    """A real view with the synthetic scene, or a skip when GL is not buildable."""
+    from orisys_studio.scene3d.view import Scene3DView
+
+    view = Scene3DView()
+    if not view.available:
+        view.close()
+        pytest.skip("no GL binding here")
+    if not view.use_scene(synthetic.poc_scene(), source_id="poc-live"):
+        view.close()
+        pytest.skip("the synthetic scene was refused")
+    view.set_enabled(True)
+    return view
+
+
+def test_a_packet_that_cannot_claim_its_field_marks_the_measurement_stale(qt_app):
+    """R2 through the view: the refusal used to be dropped on the floor.
+
+    ``snapshot()`` returning ``None`` left the pane claiming ``live`` about a picture
+    nothing was producing. Now the reason travels to the coordinator *and* back out
+    to the pane.
+    """
+    view = _stale_scene_view(qt_app)
+    try:
+        packet = ui_check._fake_packet(1)
+        packet.flow_valid = False
+        packet.invalid_reason = "compute: RuntimeError: boom"
+        view.submit_packet(packet)
+
+        coordinator = view.coordinator
+        assert coordinator is not None
+        assert coordinator.state == "stale", "a refused field kept reporting live"
+        assert coordinator.last_diagnostic is not None
+        assert coordinator.last_diagnostic.code == "field_stale"
+
+        view.tick()
+        assert view.last_diagnostic is not None
+        assert view.last_diagnostic.code == "field_stale", (
+            "the pane never learned why the measurement stopped"
+        )
+        assert view.panel is not None
+        assert view.panel.state_label.text() not in ("", "scene3d.state_stale"), (
+            "the stale state has no operator-facing sentence"
+        )
+    finally:
+        view.close()
+
+
+def test_an_unstated_field_is_refused_rather_than_assumed(qt_app):
+    view = _stale_scene_view(qt_app)
+    try:
+        packet = ui_check._fake_packet(1)
+        packet.flow_valid = None
+        view.submit_packet(packet)
+        coordinator = view.coordinator
+        assert coordinator is not None
+        assert coordinator.state == "stale"
+        assert coordinator.last_diagnostic is not None
+        assert coordinator.last_diagnostic.code == "field_unverified"
+    finally:
+        view.close()
+
+
+def test_a_fresh_field_reaches_the_screen_and_clears_the_stale_state(qt_app):
+    view = _stale_scene_view(qt_app)
+    try:
+        shape = tuple(view.assets.shape_hw)
+        packet = ui_check._fake_packet(1)
+        packet.flow = np.full((*shape, 2), 0.5, dtype=np.float32)
+        view.submit_packet(packet)
+        assert view._snapshot_diagnostic() is None, "a stated, fresh field was refused"
+        coordinator = view.coordinator
+        for _ in range(60):
+            view.tick()
+            if coordinator is not None and coordinator.state == "live":
+                break
+            time.sleep(0.01)
+        assert coordinator is not None and coordinator.state == "live", coordinator.state
+    finally:
+        view.close()
+
+
 # ------------------------------------------------------- stage 5: the record block
 def test_a_recording_says_what_the_3d_pane_was(
     make_window, next_record_root, write_poc, qt_app, monkeypatch
@@ -763,6 +847,9 @@ def test_every_run_gets_a_new_generation(make_window, qt_app):
             packet = ui_check._fake_packet(1)
             packet.flow = np.full((*shape, 2), 0.5, dtype=np.float32)
             view.submit_packet(packet)
+            assert view._snapshot_diagnostic() is None, (
+                "the adapter refused the second session's packet"
+            )
             assert view.coordinator.stale_frames == 0, (
                 "the second session's frames were refused as stale"
             )