Add body-camera timeline to the shift review

- New src/game/ui/event_timeline.gd flattens every recorded incident event
  (ADR-0005) into one time-ordered list and shows time, person, and a one-line
  summary. Step with Left/Right or the buttons; Esc returns to the review. No live
  3D replay in this first version.
- Shift review gains a "Body camera timeline" button that hands the review to the
  timeline; the review dim is hidden while it is open (stacked overlays made the
  screen nearly black) and restored on close.
- ShiftCoordinator records started_at_ms so the review can stamp events as mm:ss.
- 8 new string keys for the timeline UI and the review button.

Tests/docs
- Headless suite 113 -> 120 (test_event_timeline.gd), new smoke_timeline.gd that
  opens the timeline from the review, steps through every event, and closes back.
- README, TODO section moved to DONE, MEMORY notes. Version 0.2.6.

content/strings.en.json

@@ -68,5 +68,13 @@
   "wand.recharge": "Wand scanner is recharging…",
   "review.responder": "Responder outcomes: %s",
   "review.investigations": "Investigations: %s",
-  "review.none": "none"
+  "review.none": "none",
+  "timeline.title": "Body Camera Timeline",
+  "timeline.position": "Event %d of %d",
+  "timeline.empty": "No recorded events this shift.",
+  "timeline.prev": "◀ Previous",
+  "timeline.next": "Next ▶",
+  "timeline.close": "Close",
+  "timeline.hint": "Left/Right step through events · Esc closes · no live replay yet",
+  "review.timeline_button": "Body camera timeline"
 }