docs(fork): record long-running sync discipline

[yansigit]

Summary

• Add a shared, immutable-SHA state ledger and exact-head failure diagnosis loop for long-running upstream syncs.
• Record workflow, bot, ancestry, trust-boundary, controller, and definition-of-done rules so operators can resume safely across devices and sessions.

Verification

• bun run typecheck
• bun run test --dots (16,130 parallel tests plus all serial lanes; 0 failures)
• bun run privacy:scan
• git diff --check origin/dev...HEAD
• Focused independent review completed with no remaining findings.

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed.
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults.

[github-actions]

✅ Deterministic PR hygiene checks passed.