docs: link repository and public demo

[jack-arturo]

Summary

• link the visible CottageCode header to the GitHub repository
• link and explain the static public sample village
• document the interactive observatory, music, and nighttime features

Validation

• npm test
• README local-link validation

Notes

• Part 6 of 6; stacks on feat/moonlit-bedtime.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-15T06:48:08.307814Z	8fddaf0	New commits

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[jack-arturo]

Babysit ready. Verified green at 83953e5b3b495c8d741b0b000814e151689077b3.

Codex completed its automatic review cleanly on this head (👍); no active Codex review threads remain. CI smoke passed, npm test passed (203 tests), and the PR is mergeable. No merge was performed.