revert: undo chained/seed-grown track 5 frames, back to b71f1d4

Reverts 1530bbc and 9c95a4a. Track 5 Frames sends the drawn box unchanged to
all five frames - no chaining, no growth. Both were rejected: chaining let a
wrong read on one frame poison the next, and growth was an attempt to follow a
moving object that the user did not want.

REQ-189, ui-spec and tasks.md return to the b71f1d4 wording.

docs/requirements.md

@@ -170,20 +170,13 @@ changes.
   one object and the model produces its shape.
 - **REQ-189** — In the review editor, the user can push the **selected shape's** box forward
   with *Track 5 Frames* (`[T]`): the next five frames each get their own REQ-043 box-assist
-  run, and the shape is written as `source=manual`. Both geometry types work — a bbox shape
-  supplies its own box, a polygon is reduced to its bounding box. Runs are **independent**:
-  every frame is seeded from the drawn shape and never from another run's result, so a wrong
-  read on one frame cannot carry into the ones after it. The first frame uses the drawn box
-  untouched; frames 2–5 use it grown about its centre by ×1.5, giving a moving object room
-  to be inside the seed window. A frame SAM3 refuses (nothing inside the box) is reported and
-  the remaining frames still run. Nothing selected, an unusable shape, or the last frame says
-  so instead of doing nothing. Consequence accepted: without chaining there is no size or
-  position readjustment between frames, so a fast-moving object can still leave the seed
-  window — denser extraction (higher fps) or a video-propagation requirement (not yet
-  written) is the fix. This is
-  one-shot hand-off across the next frames, **not** propagation of drawn exemplars (which
-  stays a non-goal): nothing is tracked frame-to-frame with a motion model, and the runs
-  share no state between invocations.
+  run, seeded with that box, and the shape is written as `source=manual`. Both geometry types
+  work — a bbox shape supplies its own box, a polygon is reduced to its bounding box. Each
+  frame is an **independent** run: a frame SAM3 refuses (nothing inside the box) is reported
+  and the rest still run; nothing selected, an unusable shape, or the last frame says so
+  instead of doing nothing. This is one-shot hand-off across the next frames, **not**
+  propagation of drawn exemplars (which stays a non-goal): nothing is carried frame to frame,
+  and the runs do not depend on each other.
 - **REQ-044** — All annotations and review statuses are **persistent** — they survive a
   server restart, unlike today's in-memory sessions.
 - **REQ-045** — Review progress is visible (e.g. "120/300 reviewed"), and a batch can only

docs/tasks.md

@@ -1405,23 +1405,6 @@ read it.
    (accent border + glow) — no CSS added; **browser eyeball still owed by the user**
    (375 px 2-col wrap, long class names).
 
-## Task — Track 5 Frames follows a moving object (REQ-189) `[DONE]`
-
-1. Root cause: `trackForward` sent the **same box** to all 5 frames, and batch 19 was
-   extracted at **fps 0.5** (one frame every 2 s, `batches.fps`) — a truck entering frame
-   outruns a static seed. First attempt chained each run's result into the next frame's seed;
-   that let a wrong read on one frame carry into the following ones, which the user rejected
-   as poisoning. Final shape: runs are **independent again**, every frame seeded from the
-   drawn shape, frames 2–5 grown ×1.5 about its centre (`SEED_GROWTH`, `growBox`) for motion
-   tolerance. Geometry handling moved to module-level `shapeBox()`.
-   → verify: **[DONE]** `npm run build` green; no frame's seed derives from a previous result
-   (`seed` reassignment removed, grep confirms `firstBox` is the only seed source); first frame
-   un-grown so the stationary case keeps exact precision; growth ×1.5 total size (not 2×);
-   busy guard still blocks double-writes. **Moving-object behaviour needs the user's GPU
-   run** — and without chaining, a fast-moving truck may still leave the seed window; fix is
-   re-extract at 2 fps (*Trim → frames per second*) or a video-propagation requirement
-   (not yet written; `sam3_video_inference.py` already has `propagate_in_video`).
-
 ## Task — Track 5 Frames works at all (REQ-189) `[DONE]`
 
 1. `ReviewPage.jsx:trackForward` read `geometry.coordinates` — a key the backend never emits

docs/ui-spec.md

@@ -989,21 +989,13 @@ previous geometry** and shows the error. Same optimistic-with-rollback pattern f
 - *Copy Prev* copies every annotation from frame `n-1` onto this frame (one POST per shape);
   disabled at index 0 or when the previous frame is empty.
 - *Track 5 Frames* takes the selected shape's bounding box and runs SAM3 assist on the next 5
-  frames with it — the first with that box exactly, the rest with it grown (see below). Works
-  for both geometry types: a bbox shape supplies its own box, a polygon
+  frames with it. Works for both geometry types: a bbox shape supplies its own box, a polygon
   is reduced to its bounding box. Nothing selected, an unusable shape, or the last frame
   says so in the error slot instead of silently doing nothing; a frame SAM3 refuses (nothing
   inside the box) does not stop the rest — the banner then **starts** with `Tracked N of M`
   (M = frames actually ahead, ≤ 5) followed by the per-frame failures. A second press while
   a run is in flight is ignored. Shapes are written `source=manual`, exactly as a hand-drawn
-  one.
-  Runs are **independent**: every frame is seeded from the drawn shape, never from another
-  run's result, so a wrong read on one frame cannot poison the ones after it. The first frame
-  uses the drawn box exactly; frames 2–5 use it grown ×1.5 about its centre so a moving object
-  still fits the seed window. A refused frame does not stop the rest. Because nothing carries
-  between frames there is no size/position readjustment — a fast-moving object can still
-  outrun the seed; only denser frame extraction (higher fps) or real video propagation fixes
-  that (REQ-189).
+  one (REQ-189).
 
 **Quick reclass bar** appears whenever a shape is selected: one button per class
 (`[n] name`, class-coloured) plus *Delete [Del]*.

frontend/src/pages/ReviewPage.jsx

@@ -9,38 +9,6 @@ import ReviewSidebar from '../components/ReviewSidebar'
 import ExemplarFilterPanel from '../components/ExemplarFilterPanel'
 import useExemplarPool from '../hooks/useExemplarPool'
 
-// How much bigger the seed box gets for each frame after the first, so the
-// object has room to have moved. Hand-tuned, not learned (REQ-189). The box
-// always derives from the drawn shape — never from a previous run's result.
-const SEED_GROWTH = 1.5
-
-// SAM3 assist wants one normalized [x0, y0, x1, y1] box (REQ-043). A bbox
-// shape already is that; a polygon is reduced to its bounding box.
-function shapeBox(geometry) {
-  const pts = geometry?.points
-  if (geometry?.type === 'bbox' && pts?.length === 4) return pts
-  if (geometry?.type === 'polygon' && pts?.length) {
-    let minX = 1, minY = 1, maxX = 0, maxY = 0
-    for (const [x, y] of pts) {
-      if (x < minX) minX = x
-      if (x > maxX) maxX = x
-      if (y < minY) minY = y
-      if (y > maxY) maxY = y
-    }
-    return [minX, minY, maxX, maxY]
-  }
-  return null
-}
-
-function growBox([x0, y0, x1, y1], k) {
-  const cx = (x0 + x1) / 2
-  const cy = (y0 + y1) / 2
-  const hw = ((x1 - x0) * k) / 2
-  const hh = ((y1 - y0) * k) / 2
-  const clamp = (v) => Math.min(1, Math.max(0, v))
-  return [clamp(cx - hw), clamp(cy - hh), clamp(cx + hw), clamp(cy + hh)]
-}
-
 export default function ReviewPage({ batchId: rawBatchId, projectId, onProject }) {
   const [batch, setBatch] = useState(null)
   const [project, setProject] = useState(null)
@@ -399,8 +367,23 @@ export default function ReviewPage({ batchId: rawBatchId, projectId, onProject }
       return
     }
 
-    const firstBox = shapeBox(current.geometry)
-    if (!firstBox) {
+    // SAM3 assist wants one normalized [x0, y0, x1, y1] box (REQ-043). A bbox
+    // shape already is that; a polygon is reduced to its bounding box.
+    const geometry = current.geometry
+    let box = null
+    if (geometry?.type === 'bbox' && geometry.points?.length === 4) {
+      box = geometry.points
+    } else if (geometry?.type === 'polygon' && geometry.points?.length) {
+      let minX = 1, minY = 1, maxX = 0, maxY = 0
+      for (const [x, y] of geometry.points) {
+        if (x < minX) minX = x
+        if (x > maxX) maxX = x
+        if (y < minY) minY = y
+        if (y > maxY) maxY = y
+      }
+      box = [minX, minY, maxX, maxY]
+    }
+    if (!box) {
       setError('That shape has no usable box — Track 5 Frames needs one.')
       return
     }
@@ -417,15 +400,8 @@ export default function ReviewPage({ batchId: rawBatchId, projectId, onProject }
       const failures = []
       for (let i = 0; i < ahead.length; i++) {
         const targetFrame = ahead[i]
-        // Every frame is seeded from the drawn box, never from a previous
-        // result, so a bad read on one frame cannot carry into the next.
-        // Frames 2-5 get it grown about its centre — the object has had
-        // time to move by then.
-        const seedBox = i === 0 ? firstBox : growBox(firstBox, SEED_GROWTH)
         try {
-          await api.assist(targetFrame.id, {
-            box: seedBox, class_id: current.class_id,
-          })
+          await api.assist(targetFrame.id, { box, class_id: current.class_id })
           tracked++
           patchFrameLocally(targetFrame.id, { annotation_count: (targetFrame.annotation_count ?? 0) + 1 })
         } catch (exc) {