allow switching the detect scene of a debug replay camera without a restart

- show the scene field in the replay detect settings
- drop the replay camera's cached model on a detect change so the refresh recycle picks up the new scene's model
- recreate the tracked object state on refresh when the camera's model changed
- reject a scene no model can serve with a 400 instead of crashing the tracker and maintainer threads
- size each camera's detection input shm for the largest model and recreate leftover smaller segments, so a camera re-added under a larger model no longer overflows it
- ignore event ends for objects already dropped by a state reset

web/src/components/config-form/section-configs/detect.ts

@@ -240,14 +240,14 @@ const detect: SectionConfigOverrides = {
   },
   replay: {
     restartRequired: [],
-    fieldOrder: ["width", "height", "fps"],
+    fieldOrder: ["scene", "width", "height", "fps"],
     fieldGroups: {
       resolution: ["width", "height", "fps"],
     },
     hiddenFields: [
       "enabled",
       "enabled_in_config",
-      "scene",
+      hideSceneWithoutChoice,
       "min_initialized",
       "max_disappeared",
       "annotation_offset",