Add content-addressed Cloudflare canonical restore packs

[chubes4]

Summary

Replace per-file canonical cold hydration with one deterministic, content-addressed restore-pack read while preserving canonical R2 objects as authority.

What changed

• Persist and strictly validate deterministic restore packs; hydrate pack-backed revisions through one R2 object read while retaining bounded legacy manifest hydration; add fail-closed corruption coverage and restart evidence for Durable Object and D1 coordinators.

How to test

1. Run npm run test:cloudflare-runtime; expect Cloudflare unit and contract tests plus TypeScript pass.
2. Run npm run cloudflare:local-gate; expect Durable Object restart proves one restore-pack read and no legacy object hydration.
3. Run npm run cloudflare:local-gate:d1; expect D1 restart proves one restore-pack read and no legacy object hydration.

Compatibility

Existing manifests without restore-pack metadata continue through bounded authoritative object hydration. Referenced missing, corrupt, or divergent packs fail closed. Canonical Markdown, upload, and wp-content objects remain independently written and authoritative.

Evidence

• Base unchanged since verification: main remains at bfc6ef7.
• Reviewer-resolvable evidence from source_refs[0]: Add content-addressed Cloudflare canonical restore packs #2135
• Verified finalization base: main at bfc6ef7
• cloudflare-runtime: passed (Full Cloudflare tests and TypeScript passed) (Passed)
• d1-restart: passed (One-pack restart hydration passed; cold 602ms, warm 4ms) (Passed)
• durable-object-restart: passed (One-pack restart hydration passed; cold 621ms, warm 4ms) (Passed)

AI assistance

• AI assistance: Yes
• Tool(s): Homeboy (OpenCode)
• Model: openai/gpt-5.6-sol
• Used for: I inspected the existing Cloudflare persistence and hydration paths, implemented the restore-pack contract, hardened integrity and extraction bounds after reviewing the diff, added behavioral coverage, and interpreted the local restart evidence; a second OpenCode review found no further code changes.

Source relationships

• Closes Add content-addressed Cloudflare canonical restore packs #2135