feat: Annotation panel

[tommyjtl]

Note

Medium Risk
Adds a new persisted annotations feature (new storage keyspace + export) and threads it through the replay workspace/menubar, plus touches multiple timing-sensitive video/IK hooks (seeking, memoization, effects) which could affect interaction correctness.

Overview
Adds an Annotations workflow to replay comparisons: users can create per-video annotations, set frame/time ranges via sliders, apply label taxonomy + notes, and filter the list by frame range in the new AnnotationPanel.

Introduces useAnnotations with localStorage persistence keyed by the comparison storageKey, plus a new app/lib/annotations export schema and menubar actions to toggle annotation mode and export annotations per video.

Includes several interaction/stability refactors: converts a number of “latest props in refs” patterns to useLayoutEffect (e.g., TrajectoryOverlay, VideoDropzone, useIKDrag), restructures MouseControlPanel canvas animation handling, improves useKeyMoments active-slider resolution, and normalizes useVideoFps/useOverlaySettings state derivations.

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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Stale hidden tracks cause wrong toggle button label

Medium Severity

The hook returns the raw hiddenTrajectoryTrackNames state instead of effectiveHiddenTrajectoryTrackNames. The old useEffect that pruned stale entries from state was replaced by a derived useMemo, but only visibleTrajectoryTrackNames uses the filtered value internally. OverlaySettingsPanel checks hiddenTrajectoryTrackNames.length === 0 for allTracksVisible, so stale track names from previously-removed metadata cause the "Show All"/"Hide All" button to display the wrong label even when all available tracks are visible.

 

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