8bb18fa201
Establish book-playback-timeline as the sole playback owner driving the scene through formal webgl-book:* events (not the BookLabDebug surface), with a single reveal clock in the scene render loop and webgl-page-cache as the only texture cache. Remove the legacy dual playback path and the ownsPageFlipCommit gating. Fixes: - Flip page detached/folded at the spine: restore the raw page-cap line for flip geometry (matches the prototype/pre-regression), removing normalizeFlipLineToVisiblePage which moved the pivot off the spine arc. - Flip textures: distance-based UVs (no horizontal compression), direction-aware face material (source on the camera-facing side), source meta derived from the visible spread (manual flips), prewarm shape fix. - Reveal: flash removed on the static page and the flip back surface; spanning blocks rebuild the reveal plan at activate and continue the reveal on the next spread after the fill flip. - Cache staleness is contentVersion-primary; nav clamps to spreadCount. Docs updated to describe the intended single-owner architecture. Regression checks updated to match. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>