Timeline widget with:
- Header: play/pause + reset + duration drag + loop checkbox
- Ruler: 0.5s ticks, scrub via click+drag
- Tracks: horizontal rows with diamond-shaped draggable keyframes
- Playhead: vertical primary_light line + ruler triangle marker
State and types:
- Keyframe { time, value, ease }
- Track { name, vector<Keyframe> }
- TimelineState { tracks, current_time, duration, playing, loop }
Pure functions:
- track_value_at(track, t): interp between keys, ease applied via the
destination keyframe (Maya/AfterEffects convention)
- timeline_update(state, dt): advance current_time, wrap or saturate
Render with fn_tokens for visual coherence with the rest of the design
system. Keys are sorted by time on every changed frame to keep order
consistent during drag.
egutierrez