fix(ce-proof): update HITL flow for Proof v2

[tmchow]

Summary

ce-proof now teaches agents the Proof v2-native HITL workflow: read only review comments, make narrow content edits through /edit/v2, batch thread replies/resolutions, and reserve whole-document rewrites for true last-resort cases. This should make Proof review loops faster and safer while avoiding the stale-token, duplicate-mark, and full-rewrite habits that came from the v1-era contract.

The mutation examples now match Proof v2's stricter contract: /ops examples include Idempotency-Key, successful writes chain the next mutationBase.token, and retries that rebuild the body with a fresh baseToken mint a fresh key instead of tripping IDEMPOTENCY_KEY_REUSED.

What changed

• Reframes HITL content edits around find_replace_in_doc and block-level /edit/v2, with suggestion.add reserved for visible track-change cases and rewrite.apply documented as last resort.
• Adds efficient comment handling through state?kinds=comment, batched /ops replies/resolves, and comment.reply with resolve: true.
• Corrects copy-paste examples for Proof v2 mutation safety, including token chaining, idempotency keys on /ops, exact-body retry semantics, and consistent ai:compound-engineering bridge identity.
• Updates ce-brainstorm, ce-ideate, and ce-plan handoff wording so upstream skills no longer promise tracked suggestions as the default HITL edit path.

Verification

• bun run release:validate
• bun test tests/frontmatter.test.ts
• bun test tests/release-metadata.test.ts
• git diff --check

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