Fix motion capture UI freezes: throttling, async camera open/scan, stale poll

Several compounding freeze sources in plugins/motion_capture/:
- tracker.py: _run_real had no frame-rate cap independent of the camera's
  configured fps (up to 120fps/2560x1440 was possible), and no bound on
  consecutive failed reads — a camera that "opens" (cv2 isOpened() can lie,
  seen with Windows MSMF/obsensor) but never actually delivers frames would
  get hammered forever. Added a 20Hz processing cap, a real test-read before
  committing to a camera, and a give-up-after-30-failures fallback to
  simulation.
- tracker.py/device.py: cv2.VideoCapture() opening a real camera is a slow,
  blocking call — CameraTracker.start() used to do this synchronously on
  the caller's thread, which froze the whole app when ProfileManager.apply()
  called it during profile load. Now runs on the background thread; status
  reporting (CameraDevice) moved to an on_result callback since the caller
  can no longer learn the outcome synchronously.
- window.py: the Camera View preview ran a 30Hz GUI-thread timer doing a
  full-frame copy + QImage/QPixmap rebuild every tick unconditionally (no
  visibility check) — dropped to 10Hz and skips entirely when hidden.
  Camera enumeration (list_cameras(), up to 8 sequential cv2.VideoCapture
  probes) also ran inline in the window constructor, blocking it open the
  same way camera_panel.py's CameraScanThread already avoided for the Add
  Device dialog — moved to the same async pattern here.

config_window.py: separately, ConfigWindow._dev_poll (device status label
refresh) was stopped in closeEvent and never restarted, since MainWindow
reuses the same ConfigWindow instance across opens — invisible before
because connect() was synchronous, but with the above change a device can
sit in CONNECTING for a while, and a stale poll made that look stuck
forever after reopening the window. Restart it in showEvent.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

1 files changed, 11 insertions, 2 deletions

diff --git a/ui/windows/config_window.py b/ui/windows/config_window.py
index 34cc789..604b6ed 100644
--- a/ui/windows/config_window.py
+++ b/ui/windows/config_window.py
@@ -24,7 +24,7 @@ from PyQt6.QtWidgets import (
     QDoubleSpinBox,
 )
 from PyQt6.QtCore import Qt, pyqtSignal, QTimer
-from PyQt6.QtGui import QCloseEvent, QColor
+from PyQt6.QtGui import QCloseEvent, QColor, QShowEvent
 
 from devices.device_registry import DeviceRegistry
 from core.acquisition import AcquisitionEngine
@@ -535,7 +535,16 @@ class ConfigWindow(QWidget):
         if idx == 2:
             self._plot_tab.refresh_channels()
 
-    # ── Close ────────────────────────────────────────────────────────────────
+    # ── Show / Close ─────────────────────────────────────────────────────────
+
+    def showEvent(self, e: QShowEvent):
+        # closeEvent stops this poll; MainWindow reuses this same ConfigWindow
+        # instance across opens (doesn't recreate it), so without restarting
+        # here, reopening after a prior close leaves device status frozen at
+        # whatever it was at close time — e.g. stuck showing "Connecting…"
+        # for an async-connecting device like the motion capture camera.
+        self._dev_poll.start()
+        super().showEvent(e)
 
     def closeEvent(self, e: QCloseEvent):
         self._dev_poll.stop()