Clarify provisional Ghost memory guidance

[nahiyankhan]

🤖 AI-agent-authored PR.

Summary

• Add guidance for when accepted Ghost fingerprint memory is silent: proceed from local evidence when safe, but label that reasoning provisional and non-Ghost-backed.
• Carry the guidance through installed skill docs, context bundle prompts, review commands, and advisory review packets.
• Extend CLI tests to lock the emitted prompt surfaces and update the changeset copy.

Verification

• pnpm exec biome check packages/ghost/src/review-packet.ts packages/ghost/src/scan/context/package-review-command.ts packages/ghost/src/scan/context/package-writer.ts packages/ghost/test/cli.test.ts
• pnpm exec vitest run packages/ghost/test
• pre-push hook: pnpm build, pnpm check, pnpm test