Improve motion direction and beat-aware render review

[squatarn]

Broad motion-graphics briefs need a consistent visual language and deliberate timing across scenes. The previous guidance left those decisions implicit, while evenly spaced contact sheets could miss a fast handoff or landing.

This change:

• Defines shared shape/colour meanings, visual tokens, named beats, coupled motion, and seven practical animation lenses, with restraint appropriate to clean graphics.
• Adds exact beat and adjacent-frame sampling, selectable review backgrounds, optional H.264 playback copies, and a JSON frame map. Decodes the master once for sampling.
• Preserves unrelated files in review folders and rejects source-overwriting paths. Counts decoded video frames when metadata is missing, including when audio is longer than video.
• Clarifies approved-style precedence, local-font use, current Remotion reference routing, and isolated harness maintenance.

Validation: six FFmpeg-backed tests pass (33 assertions); bun run lint, ESLint for both review scripts, and git diff --check pass. Exercised the tool against an existing 1080x1920, 24fps ProRes master and inspected its contact sheet. Skill frontmatter was checked with Bun YAML; the bundled Python validator could not run because PyYAML is absent.

No dependencies, current compositions, assets, saved preferences, or registry entries changed. Creative guidance still needs judging on newly authored work; the technical tests do not establish a visual-quality improvement.