Reset per-game reveal state on new game so reveal animates over cached content

Starting a new game reuses block ids (1,2,3...). The reveal clock's per-block
start times (activeRevealBlockStarts in the lab) and the renderer's animation/
revealed sets are keyed by block id and were never cleared on a client reset, so
a new game over already-cached content inherited the previous run's start times.
beginPageReveal then computed a huge elapsed and the shader treated the reveal as
already complete — showing everything at once instead of animating.

resetClientPlaybackAndDisplay (run on new game and restore) now emits
story:client-reset; the lab clears activeRevealBlockStarts/pending reveal state,
the texture renderer clears active animations and revealed-block ids, and the
timeline invalidates prepared segments. So each game starts with a clean reveal
clock.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/js/book-playback-timeline-module.js

@@ -99,6 +99,10 @@ class BookPlaybackTimelineModule extends BaseModule {
         });
         this.addEventListener(document, 'webgl-book:page-count-changed', this.invalidatePreparedSegments);
         this.addEventListener(document, 'story:history-restoring', this.invalidatePreparedSegments);
+        this.addEventListener(document, 'story:client-reset', () => {
+            this.invalidatePreparedSegments();
+            this.activeSegment = null;
+        });
         window.BookPlaybackTimeline = this;
         this.reportProgress(100, 'Book playback timeline ready');
         return true;