feat: per-class exemplar preview, class hide toggle, container NMS flag (REQ-182, REQ-183, REQ-184)

docs/requirements.md

@@ -95,8 +95,11 @@ changes.
 
 - **REQ-030** — Once frames are extracted, the system runs SAM3 over all of them using each
   class's prompt, as a background job with progress and cancellation.
-- **REQ-031** — Detections that overlap across prompts are deduplicated (greedy IoU NMS), so
-  one object is not labelled as two classes at once.
+- **REQ-031** — Detections that overlap across prompts are deduplicated (greedy IoU NMS
+  across classes, threshold = the lower-scoring detection's class IoU override if set,
+  else the job's global IoU), so one object is not labelled as two classes at once. A
+  detection contained inside a higher-scoring box of a class marked container (REQ-184)
+  is never removed by that box — containment is not overlap.
 - **REQ-032** — The confidence threshold is configurable per job.
 - **REQ-181** — Auto-annotation accepts per-class overrides of confidence, IoU and minimum box
   fraction on top of the job's global values; classes without an override use the global
@@ -122,8 +125,16 @@ changes.
   re-run immediately, and can be undone or cleared. Exemplars are a **tuning aid only**: they
   are never written as annotations and never carried into the batch job, because SAM3's
   geometric prompts pool features from the current image — replaying them on another frame
-  would ask about whatever happens to sit at those coordinates there. They belong to exactly
-  one class, so a new frame or a new active class discards them.
+  would ask about whatever happens to sit at those coordinates there. Each class keeps its own
+  pool on the current frame: switching the active class shows that class's pool instead of
+  discarding the others, and a new frame discards them all.
+- **REQ-182** — The auto-annotate preview is **per class and accumulates**. While at least one
+  class has example boxes on the previewed frame, the preview shows only the classes that have
+  examples, each conditioned on its own pool; re-drawing one class's example refreshes only
+  that class's predictions and leaves the other exemplared classes' results on screen. Classes
+  without examples contribute nothing while any example exists, and clearing the last example
+  restores the plain full-set preview. The preview and the batch job still use the same
+  thresholds and per-class overrides.
 
 ## E. Review & correction
 
@@ -174,6 +185,19 @@ changes.
 - **REQ-180** — In the manual review editor, each class row can clear that class's shapes on
   the **current frame only** (REQ-046 stays batch-wide). One click, no confirmation dialog;
   the next frame is untouched.
+- **REQ-183** — In the manual review editor, each class row has a **hide toggle**. A hidden
+  class's shapes disappear from both the annotation canvas and the "Shapes on this frame"
+  list — not selectable, not marquee-selectable, not deletable while hidden — while the class
+  row keeps its real per-frame count and its eye state, so what is hidden stays visible as
+  state. The choice is session state: it survives frame changes, resets when the review page
+  is left, and never touches stored data.
+- **REQ-184** — A class can be marked as **container** (persisted on
+  `project_classes.container`, edited next to the per-class overrides in the auto-annotate
+  modals). When the cross-class NMS of REQ-031 compares another class's box against a
+  higher-scoring box of a container class, containment is not overlap: if at least 90% of
+  the smaller box's area lies inside the container's box, both survive. The flag changes
+  nothing else — unmarked classes are governed by IoU alone — and preview and batch job
+  read the same stored flag.
 
 ## E4. Live counting preview