[codex] Simplify Ghost memory around generation packets

[nahiyankhan]

Summary

• Make .ghost/fingerprint.yml the canonical Ghost memory source, with Git review as the approval boundary and optional inventory/cache as source material rather than memory.
• Rework scan/status, context-bundle, review-command, docs, and the installed skill guidance around product prose, curated exemplars, and active checks.
• Add first-class exemplar and active-check grounding to generation packets, including typed check refs and validation for missing or inactive refs.
• Remove the remaining proposal-era surfaces, templates, exports, and docs from the public bundle and legacy ghost-core.
• Keep the curl install bundle deterministic by adding check-install-bundle, wiring it into pnpm check, and updating the install manifest.

Validation

• pnpm build
• pnpm check
• pnpm test