docs: add playable geoptimize promo

[cucuwang]

Problem and change

Adds the approved 30-second geoptimize promo with editable sources and original music. Embeds v2 in the repository README and video README so visitors can play it on GitHub.

Validation and impact

• Tests/build pass; all 10 head checks succeeded, including Node 22/24, Node 26 preview, release reproducibility, Action contracts, README checks, CodeQL and dependency review. Local syntax checks and the 900-frame layout audit passed; the MP4 decoded successfully and the README player loaded the full 30-second video.
• CLI, API, JSON and Action contracts preserved; changes are limited to README and marketing files.
• Security and dependency impact reviewed; no runtime dependencies changed. Font licenses and motion-workflow attribution are included.
• Scoring/methodology impact stated; the film uses the existing synthetic fixture and makes no search-outcome claims.
• Documentation updated with the player, download link, editable sources and validation records.
• Release/package impact stated; no version bump or npm publication. Marketing assets are outside the package file allowlist.

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