add: scan fragmented repair parts sequentially

docs/user/main-feature.md

@@ -15,7 +15,7 @@ The current user flow is:
 5. The repair case appears near the mission object and can float when the player approaches it.
 6. Press `E` or hold both fists closed for one second to move from `inspected` to `fragmented`.
 7. The mission object uses an exploded-model transition, then moves to `scanning`.
-8. The scan visual highlights the broken area and shows the `cassé.webm` prompt.
+8. The scan visual moves across the fragmented model one part at a time.
 9. In `repairing`, the case opens and several grabbable replacement parts appear near the case.
 10. Move the correct replacement part close to the install target.
 11. Press `E` on the green install target to move to `done` and show the reassembled object. Wrong parts turn the target red and cannot finish the repair.
@@ -33,7 +33,7 @@ When the player inspects the object, `RepairGame` writes `inspected` through the
 
 In `inspected`, `RepairGame` can also move to `fragmented`. The player can use the interaction key or hold both fists closed for one second. The hand-tracking path is state-based, so it does not depend on being inside a local object interaction radius.
 
-In `fragmented`, the repair object is rendered with `ExplodableModel`, then automatically advances to `scanning`. In `scanning`, a blue scan visual and the `cassé.webm` prompt are shown before the flow advances to `repairing`. In `repairing`, the case opens, several grabbable replacement parts appear, and the install target only validates the configured correct part for the active mission. In `done`, the repaired object remains visible with a completion target that plays the case exit animation before advancing the global mission progression.
+In `fragmented`, the repair object is rendered with `ExplodableModel`, then automatically advances to `scanning`. In `scanning`, the exploded model remains visible and a blue scan visual moves from part to part before the flow advances to `repairing`. In `repairing`, the case opens, several grabbable replacement parts appear, and the install target only validates the configured correct part for the active mission. In `done`, the repaired object remains visible with a completion target that plays the case exit animation before advancing the global mission progression.
 
 ## Key Files
 
@@ -44,7 +44,8 @@ In `fragmented`, the repair object is rendered with `ExplodableModel`, then auto
 - `src/components/three/gameplay/RepairMissionCase.tsx` renders the mission repair case after inspection.
 - `src/components/three/gameplay/RepairRepairingStep.tsx` renders grabbable replacement choices, correct-part placement validation, and the install trigger in `repairing`.
 - `src/components/three/gameplay/RepairPromptVideo.tsx` renders `.webm` prompts inside the 3D scene.
-- `src/components/three/gameplay/RepairScanVisual.tsx` renders the scan halo, scan line, and broken prompt.
+- `src/components/three/gameplay/RepairScanSequence.tsx` keeps the exploded model visible and advances the scan from part to part.
+- `src/components/three/gameplay/RepairScanVisual.tsx` renders the scan halo and scan line around the active part.
 - `src/hooks/gameplay/useRepairFragmentationInput.ts` handles the `inspected -> fragmented` keyboard and hand-tracking input.
 - `src/hooks/gameplay/useRepairMissionStep.ts` reads the active mission step from the game store.
 - `src/hooks/handTracking/useBothFistsHold.ts` detects the reusable two-fists hold gesture.