feat(studio): 三维视图接入产品（阶段 4：界面、生命周期与记录隔离）

- What: `Scene3DView` 装配（widget/相机/渲染器/合成器/协调器/适配器），`asset_source`
  只查找并后台加载已编译的 `.oryscene` 包，`scene3d/prefs` 持久化并**修复**显示设置，
  `ui/mesh3d_panel` 用真实容器替换占位标签（无 GL/无包/包被拒/传感器不匹配各显示一行原因），
  `main.py` 在 `QApplication` 之前选定 GL profile，`app_window` 接线：3D 作为采集线程上的
  第二个 sink、`_on_run_tick` 驱动 `tick()`、视图切换与 `closeEvent` 释放、preferences 落盘。
- Why: 阶段 4 的验收要求"三维开关不影响采集/记录/力曲线"，并把阶段 1 留下的
  "开/关三维 CSV 一致"这条补上；同时把"没有 context"从"看起来像在工作"变成可显示的终态。
- Verification: app 侧 test_scene3d_view 28 项、test_scene3d_gl_smoke 14 项（真实 GPU）、
  adapters 17 项、skeleton 4 项、stage1 24 项、coordinator 13 项、ui_smoke 86 项；
  shared 侧 contract 26 / assets 33 / package 19 / live 25；`ui_check.py` 566 项检查 0 失败
  （新增 "3D pane" 段 12 项）；`locale_check.py` 302 个字面 key 0 缺失、中英各 377 key 对齐；
  记录隔离：同一 96 帧会话挂/不挂 3D 消费者，`forces.csv` 逐字节相同、有效样本数与记录问题数相同；
  生产者预算：合成器放慢到 50 ms 时 `submit_packet` p99 < 1 ms。
- Not in this change: 示意位移（`displacement_sensor_m`）仍未接入（需 SDK lift 与已确认尺度）；
  ARM 板卡适配（按用户要求暂缓）；包签名/AES-GCM 与长时性能报告（阶段 5）；
  仓库中仍未提供 `.oryscene` 包（发布产物，且其单位与变换必须由人声明）。

apps/studio/tests/test_scene3d_gl_smoke.py

@@ -377,3 +377,184 @@ def test_the_probe_reports_this_machine_truthfully():
     assert context["profile_used"] == "desktop33"
     assert not context["software_renderer"], "the dev machine has a real GPU"
     assert report["renderer_initialized"] and report["released"]
+
+
+# ------------------------------------------------- stage 4: the assembled view
+class _Packet:
+    """The parts of an ``SdkPacket`` the finger adapter and the identity need."""
+
+    def __init__(self, frame_id: int, shape_hw: tuple[int, int], value: float = 0.5) -> None:
+        self.session_id = 1
+        self.frame_id = int(frame_id)
+        self.mono_t = float(frame_id) / 30.0
+        self.flow = np.full((*shape_hw, 2), float(value), dtype=np.float32)
+        self.raw_frame = np.zeros((4, 4, 3), dtype=np.uint8)
+
+
+@pytest.fixture(scope="module")
+def assembled_view(qt_app):
+    """A real ``Scene3DView``: pane, coordinator, composer, widget, real context."""
+    from orisys_studio.scene3d.gl_backend import configure_surface_format
+    from orisys_studio.scene3d.view import Scene3DView
+
+    configure_surface_format("desktop33")
+    view = Scene3DView()
+    if not view.available:
+        pytest.skip(f"no GL view here: {view.reason}")
+    assets = synthetic.poc_scene()
+    if not view.use_scene(assets, source_id="poc-live"):
+        pytest.skip("the synthetic scene was refused")
+    view.resize(360, 300)
+    view.show()
+    view.set_enabled(True)
+    renderer = view.gl_widget._renderer
+    painted = _pump(qt_app, view.gl_widget, lambda: bool(renderer.part_ids), timeout_s=8.0)
+    if not painted:
+        view.close()
+        pytest.skip(f"no usable GL context here: {view.gl_widget.diagnostic()}")
+    yield view, renderer, assets
+    view.close()
+    view.close()
+    qt_app.processEvents()
+
+
+def test_the_assembled_view_draws_what_the_acquisition_thread_hands_it(assembled_view, qt_app):
+    """The whole stage-4 path: packet in, pixels out, and no recording involved."""
+    view, renderer, assets = assembled_view
+    widget = view.gl_widget
+    for index in range(30):
+        view.submit_packet(_Packet(index, assets.shape_hw, value=0.4 + index * 0.05))
+        view.tick()
+        qt_app.processEvents()
+    assert _pump(qt_app, widget, lambda: view.state() in ("live", "no_data"), timeout_s=5.0)
+    assert view.state() in ("live", "no_data"), view.state()
+    stats = widget._last_stats_at and None  # stats are published on a timer
+    del stats
+    assert view.last_descriptor is not None, "the pane never learned what it is showing"
+    assert view.last_descriptor.quantity == "flow_magnitude"
+    assert view.last_descriptor.quality == "approximate"
+    drawn = _drawn(_render(widget, qt_app))
+    assert drawn.size, "the live frame was not drawn"
+
+
+def test_the_producer_side_never_waits_for_the_gpu(assembled_view, qt_app):
+    """The measured budget: the acquisition thread's own cost, with a slow composer.
+
+    This is the stage-3 property asserted through the *application's* entry point, so
+    it includes the adapter (the flow magnitude over the whole grid) and not just the
+    mailbox. The composer is slowed to 50 ms, which is far below any real frame rate:
+    frames must drop in the display and nowhere else.
+    """
+    import time
+
+    view, _, assets = assembled_view
+    coordinator = view.coordinator
+    real_composer = coordinator._composer
+
+    class Slow:
+        def compose(self, *args, **kwargs):
+            time.sleep(0.05)
+            return real_composer.compose(*args, **kwargs)
+
+        def rest_frame(self, *args, **kwargs):
+            return real_composer.rest_frame(*args, **kwargs)
+
+    coordinator._composer = Slow()
+    try:
+        samples: list[float] = []
+        for index in range(200):
+            packet = _Packet(index, assets.shape_hw, value=0.5)
+            started = time.perf_counter()
+            view.submit_packet(packet)
+            samples.append((time.perf_counter() - started) * 1000.0)
+            view.tick()
+        ordered = sorted(samples)
+        p99 = ordered[int(len(ordered) * 0.99) - 1]
+        assert p99 < 1.0, f"submit p99 was {p99:.2f} ms with a 50 ms composer"
+        assert max(samples) < 5.0, f"submit peaked at {max(samples):.2f} ms"
+        assert coordinator.superseded_frames > 0, (
+            "a 50 ms composer produced no display drops: the frame rate limiter or the "
+            "mailbox is not doing its job"
+        )
+    finally:
+        coordinator._composer = real_composer
+        # Drain the in-flight compose that the slow composer left behind.
+        deadline = time.perf_counter() + 1.0
+        while time.perf_counter() < deadline and coordinator._inflight is not None:
+            coordinator.tick()
+            time.sleep(0.01)
+
+
+def test_an_automatic_colour_scale_follows_the_frame(assembled_view, qt_app):
+    """A range taken from the data, and a fixed range that ignores it."""
+    view, renderer, assets = assembled_view
+    widget = view.gl_widget
+    assets_frame = view.assets
+    assert assets_frame is not None
+    count = int(assets_frame.sensing_part().positions_sensor_m.shape[0])
+
+    def frame_with(values: np.ndarray) -> RenderFrame:
+        return RenderFrame(
+            identity=FrameIdentity("poc-live", 1, 1, 0.0, generation=view.coordinator.generation),
+            asset_hash=assets.asset_hash,
+            geometry_id=assets.geometry_id,
+            sensing_part_id=assets_frame.sensing_part().part_id,
+            positions_sensor_m=assets_frame.sensing_part().positions_sensor_m,
+            normals_sensor=assets_frame.sensing_part().normals_sensor,
+            scalar=freeze(np.asarray(values, dtype=np.float32), dtype=np.float32),
+            valid=freeze(np.ones(count, dtype=np.bool_), dtype=np.bool_),
+            scalar_descriptor=FieldDescriptor("flow_magnitude", "px", "approximate", False),
+        )
+
+    descriptor = FieldDescriptor("flow_magnitude", "px", "approximate", False)
+    auto = DisplaySettings(
+        housing_visible=False,
+        color_scale=ColorScale(
+            descriptor=descriptor, lower=0.0, upper=1.0, lut_id="sequential", mode="automatic"
+        ),
+    )
+    fixed_wide = DisplaySettings(
+        housing_visible=False,
+        color_scale=ColorScale(
+            descriptor=descriptor, lower=0.0, upper=1000.0, lut_id="sequential", mode="fixed"
+        ),
+    )
+    ramp = np.linspace(3.0, 7.0, count)
+
+    widget.set_settings(fixed_wide)
+    widget.present(frame_with(ramp))
+    assert renderer._scalar_range is not None and renderer._scalar_range[0] > 2.0
+    flat = len(np.unique(_drawn(_render(widget, qt_app)), axis=0))
+    widget.set_settings(auto)
+    widget.present(frame_with(ramp))
+    spread = len(np.unique(_drawn(_render(widget, qt_app)), axis=0))
+    assert spread > flat, (
+        "an automatic range did not use the frame's own values "
+        f"(distinct colours: automatic {spread}, fixed 0..1000 {flat})"
+    )
+
+
+def test_the_pane_releases_its_context_and_survives_a_second_close(qt_app):
+    """`closeEvent` calls this; a second close must be a no-op, not a crash."""
+    from orisys_studio.scene3d.gl_backend import configure_surface_format
+    from orisys_studio.scene3d.view import Scene3DView
+
+    configure_surface_format("desktop33")
+    view = Scene3DView()
+    if not view.available:
+        pytest.skip("no GL view here")
+    if not view.use_scene(synthetic.poc_scene(), source_id="poc-close"):
+        pytest.skip("the synthetic scene was refused")
+    view.resize(200, 160)
+    view.show()
+    view.set_enabled(True)
+    renderer = view.gl_widget._renderer
+    if not _pump(qt_app, view.gl_widget, lambda: bool(renderer.part_ids), timeout_s=8.0):
+        view.close()
+        pytest.skip("no usable GL context here")
+    view.close()
+    assert not renderer.is_initialized
+    assert not renderer.part_ids, "closing the pane left GPU buffers behind"
+    view.close()
+    view.close()
+    qt_app.processEvents()