Fix spanning-paragraph reveal pacing (right page no longer consumes full TTS)

A paragraph that overflows the right page onto the next spread revealed its single
right-page line over the entire TTS, then timed out (timeline-reveal-commit-timeout)
and only flipped after the whole narration. Two root causes:

- At activate the reused lookahead segment played a sentence instance whose animation
  word-timings were lost (wordTimings=[], totalDuration=0), so reveal timing fell back
  to an area estimate spanning the full TTS. Snapshot the timings at prepare and restore
  them at activate.
- Reveal duration was distributed by ink area, but just-paginated continuation lines
  have ~0 area, so the one right-page line received the whole duration. Distribute by
  word count (reliable) with area as fallback.

Now the right page reveals only its word share (~2.7s for a 6/55-word line), commits,
and flips while TTS continues; the continuation animates on the next spread. Also
rewrote the right-reveal wait to a single timer + commit/fast-forward listeners with
cleanup, removing the stray timeline-reveal-commit-timeout.

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

scripts/check-webgl-book-lab.js

@@ -165,7 +165,7 @@ const checks = [
     ['webgl page text textures avoid mipmap generation', /function configurePageCanvasTexture/.test(source) && /texture\.minFilter = THREE\.LinearFilter/.test(source) && /texture\.generateMipmaps = false/.test(source)],
     ['webgl reveal shader masks against a base-page texture instead of flat color blocks', /bookRevealBaseMap/.test(source) && /bookRevealUseBaseMap/.test(source) && /revealBaseColor/.test(source) && /baseCanvas/.test(textureRendererSource)],
     ['webgl reveal shader masks antialiased ink and uses smooth line-dominant scan', /smoothstep\(0\.52, 0\.9, luminance\)/.test(source) && /local\.x \* 0\.96/.test(source) && /bookRevealSoftness = \{ value: 0\.025 \}/.test(source)],
-    ['webgl reveal line timings use global area timing across split-page spreads', /assignRevealTiming/.test(textureRendererSource) && /sourceSpreads/.test(textureRendererSource) && /this\.pagination\?\.spreads/.test(textureRendererSource) && /spreadIndex/.test(textureRendererSource) && /totalDuration \* \(Math\.max\(1, region\.timingArea \|\| region\.area\) \/ totalArea\)/.test(textureRendererSource) && /durationMs: sideRegions\.reduce/.test(textureRendererSource)],
+    ['webgl reveal line timings use global word-weighted timing across split-page spreads', /assignRevealTiming/.test(textureRendererSource) && /sourceSpreads/.test(textureRendererSource) && /this\.pagination\?\.spreads/.test(textureRendererSource) && /spreadIndex/.test(textureRendererSource) && /totalDuration \* \(weight \/ totalWeight\)/.test(textureRendererSource) && /durationMs: sideRegions\.reduce/.test(textureRendererSource)],
     ['webgl page format reduces only outer margins from previous value', /outerBaseIn: 0\.27/.test(pageFormatSource) && /outerThicknessFactor: 0\.015/.test(pageFormatSource) && /outerMaxIn: 0\.315/.test(pageFormatSource) && /innerBaseIn: 0\.42/.test(pageFormatSource)],
     ['webgl mode enlarges and inverts DOM overlay text without touching 2D mode', /body\.webgl-mode \{[\s\S]*font-size: 18px;/.test(styleSource) && /body\.webgl-mode \.choice-list \.choice-button/.test(styleSource) && /rgba\(246, 231, 201/.test(styleSource)],
     ['webgl choice overlay hides title clutter and prevents horizontal scrollbar', /body\.webgl-mode #page_left #game_title/.test(styleSource) && /body\.webgl-mode #page_left #start_prompt/.test(styleSource) && /overflow-x: hidden/.test(styleSource) && /book\.style\.width = 'min\(44rem/.test(webglSceneSource)],
@@ -213,7 +213,7 @@ const checks = [
     ['game loop persists webgl book state in save slots', /webglBookState: this\.getWebGLBookState\(\)/.test(fs.readFileSync(path.join(__dirname, '..', 'public', 'js', 'game-loop-module.js'), 'utf8')) && /applyWebGLBookState\(browserSave\.webglBookState\)/.test(fs.readFileSync(path.join(__dirname, '..', 'public', 'js', 'game-loop-module.js'), 'utf8'))],
     ['webgl right-page reveal flips are owned by the timeline, not the scene', !/pendingRightPageFlip/.test(source) && !/handleRevealCommittedForPageFlip/.test(source) && /waitForVisualCompletion/.test(bookPlaybackTimelineSource) && /reason: 'timeline-right-page-filled'/.test(bookPlaybackTimelineSource) && /requiresRightPageFlipAfterReveal/.test(bookPlaybackTimelineSource) && /isChoiceAwaitingPlayer/.test(bookPlaybackTimelineSource)],
     ['webgl reveal clock follows absolute playback time and continues across page flips', /activeRevealBlockStarts/.test(source) && /state\.visualElapsedMs = Math\.max\(0, now - state\.startedAt\)/.test(source) && !/Math\.min\(revealFrameDeltaMs, targetFrameDurationMs\)/.test(source) && /prewarmFlipTextures\(1, targetSpread\)/.test(source)],
-    ['webgl line reveal timing uses area-weighted regions instead of word-span timing', /lineWordCount/.test(bookPaginationSource) && /blockWordStart/.test(textureRendererSource) && /blockWordCount/.test(textureRendererSource) && /timingArea/.test(textureRendererSource) && /totalDuration \* \(Math\.max\(1, region\.timingArea \|\| region\.area\) \/ totalArea\)/.test(textureRendererSource) && !/const canUseLineWordSpans/.test(textureRendererSource)],
+    ['webgl line reveal timing is word-weighted (reliable for 0-area continuation lines) with area fallback', /lineWordCount/.test(bookPaginationSource) && /blockWordStart/.test(textureRendererSource) && /blockWordCount/.test(textureRendererSource) && /timingArea/.test(textureRendererSource) && /const useWordWeights = collectedWords > 0/.test(textureRendererSource) && /totalDuration \* \(weight \/ totalWeight\)/.test(textureRendererSource) && !/const canUseLineWordSpans/.test(textureRendererSource)],
     ['webgl flip completion defers book rebuild out of the final animation frame', /scheduledBookRebuildFrame/.test(source) && /function scheduleBookRebuild/.test(source) && /syncReadingProgressToCurrentPage\(\{[\s\S]*rebuild: 'defer'[\s\S]*reason: 'page-flip-finished'/.test(source)],
     ['webgl ordinary flip near-end uses resident target textures and defers revealing sides', /applyResidentSpreadTextures\(targetSpread, 'page-flip-near-end', \{ skipSides: flip\.deferRevealSides \}\)/.test(source) && /function applyResidentSpreadTextures\(spreadIndex, reason = 'resident-spread', options = \{\}\)/.test(source) && /const skipSides = Array\.isArray\(options\.skipSides\)/.test(source) && /residentSpreadTextures:applied/.test(source) && /spreadUpdate:state-only/.test(source)],
     ['webgl autoplay flip source prefers currently revealing visible material over resident cache', /if \(revealStateMatchesPage\(side, pageMeta\)\) return material\?\.map \|\| null/.test(source) && /revealStateMatchesPage\(sourceSide, sourcePageMeta\) \? sourceSide : null/.test(source)],
@@ -237,7 +237,7 @@ const checks = [
     ['webgl scene reports reveal commits but does not own flips and no ownership flag survives', /dispatchEvent\(new CustomEvent\('webgl-book:reveal-committed'/.test(source) && !/handleRevealCommittedForPageFlip/.test(source) && !/ownsPageFlipCommit/.test(source) && !/ownsPageFlipCommit/.test(textureRendererSource) && !/ownsPageFlipCommit/.test(bookPlaybackTimelineSource)],
     ['webgl reveal clock explicitly freezes during physical flips', /pageRevealFreezeAt/.test(source) && /state\.startedAt \+= frozenMs/.test(source) && /activeRevealBlockStarts\.set\(blockId, Number\(value\) \+ frozenMs\)/.test(source)],
     ['book playback timeline waits for right reveal only when current block is on right page', /getBlockRevealSides/.test(bookPlaybackTimelineSource) && /revealSides\.includes\('right'\) && this\.requiresRightPageFlipAfterReveal/.test(bookPlaybackTimelineSource) && /visual-completion:no-right-flip-wait/.test(bookPlaybackTimelineSource)],
-    ['book playback timeline flips at planned right-page fragment time instead of full TTS completion', /waitForPlannedRightReveal/.test(bookPlaybackTimelineSource) && /getRightRevealDurationMs/.test(bookPlaybackTimelineSource) && /segment\.revealStartedPromise/.test(bookPlaybackTimelineSource) && /Promise\.race\(\[[\s\S]*this\.waitForRevealCommit\(segment\)/.test(bookPlaybackTimelineSource)],
+    ['book playback timeline flips at planned right-page fragment time without a stray commit timeout', /waitForPlannedRightReveal/.test(bookPlaybackTimelineSource) && /getRightRevealDurationMs/.test(bookPlaybackTimelineSource) && /segment\.revealStartedPromise/.test(bookPlaybackTimelineSource) && /const timer = setTimeout\(\(\) => finish\(true\), remaining\)/.test(bookPlaybackTimelineSource) && !/waitForRevealCommit/.test(bookPlaybackTimelineSource)],
     ['book playback timeline exposes reveal lifecycle benchmark entries', /benchmarkEntries/.test(bookPlaybackTimelineSource) && /markBenchmark\('reveal-start'/.test(bookPlaybackTimelineSource) && /markBenchmark\('reveal-committed'/.test(bookPlaybackTimelineSource) && /webglBookBenchmark/.test(bookPlaybackTimelineSource)],
     ['webgl scene records reveal start and slow-frame benchmark diagnostics', /revealState:created/.test(source) && /revealStart:applied/.test(source) && /slowFrameLog/.test(source) && /getBenchmarkState/.test(source) && /webglSlowFrames/.test(source)],
     ['webgl navigation is spread-based and caps at visited/written spread', /function navigateToSpread\(/.test(source) && /function navigateBySpreadDelta\(/.test(source) && /function getMaxNavigableSpread\(\)/.test(source) && /Math\.min\(visitedSpread, spreadCount - 1\)/.test(source) && /navigateBySpreadDelta\(1\)/.test(source) && /spread <= 0 \? '0' : String\(spread \* 2 \+ 1\)/.test(source) && /currentSpread < getMaxNavigableSpread\(\)/.test(source)],