AI Implementation feature(907): Challenges Page and Challenge Solve Modal 1.03 (#49)

docs/guides/event-window.md

@@ -3,7 +3,7 @@ type: guide
 title: Event Window
 description: How the event window state machine is computed and surfaced via REST + SSE.
 tags: [guide, event, countdown, sse, state-machine]
-timestamp: 2026-07-23T01:19:00Z
+timestamp: 2026-07-23T03:09:00Z
 ---
 
 # Configuration
@@ -73,7 +73,10 @@ The store:
 3. Exposes `countdownText` (computed): `""` for `unconfigured`,
    `"Event ended"` for `stopped`, and `formatDdHhMm(seconds)` for
    `countdown` / `running`. The format helper lives in the pure module
-   `event-status.pure.ts` (`DD:HH:mm`, zero-padded).
+   `event-status.pure.ts` (`DD:HH:mm:ss`, zero-padded). The seconds
+   digit is driven by the local 1-second tick (and the SSE re-push
+   every 60 seconds) so the final minute of the countdown visibly
+   elapses second-by-second on the shell header.
 
 The header (`ShellHeaderComponent`) renders an LED with the
 `led-{state}` class so the colour reflects the current state (the