[codex] Add thresholded proposal guidance

[nahiyankhan]

🤖

Summary

• Add Proposal Threshold guidance to Ghost review prompts, context bundles, and installed skill recipes.
• Require memory-gap findings to include Memory action: none | recommend-proposal | create-proposal.
• Update initialized fingerprint policy, docs, tests, and add a patch changeset.

Validation

• pnpm exec vitest run packages/ghost/test/cli.test.ts
• pnpm test
• pre-commit hook: pnpm check + format checks
• pre-push hook: pnpm build, pnpm check, pnpm test