[laneB] M1: timeline model+clock, panel UI, stub, self-check
- timeline.js: headless clock/tracks/evaluate (transform slerp, param lerp,
clip blocks with fade-out, camera cuts, undo stack). No three/DOM import.
- tlui.js: canvas panel — ruler scrub, playhead, key add/drag/delete, clip
blocks, camera cuts, save/load with localStorage fallback. Injects own CSS.
- stagestub.js: dev Stage per PLAN §4.2 (deleted at SYNC 1).
- timeline_test.mjs: node self-check, all assertions pass.
- tldev.html: dev-only browser harness (deleted at SYNC 1).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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