feat: gate llmdoc updates on durable knowledge

[Disdjj]

Summary

• add a Stable Knowledge Gate so delta hits and reflection candidates trigger semantic review instead of automatic prose growth
• add llmdoc commit --verified <path...> for validated, unchanged docs, including meta-only finalization and changed/verified fingerprint unions
• preserve the restored Reflection Gate while requiring promoted lessons to pass the same durability test
• enforce Claude-to-Codex skill/agent body parity and version consistency in CI; bump release surfaces to 3.5.0
• converge the seven dogfood docs from about 4221 to 1479 estimated tokens while retaining decisions, invariants, failure semantics, and workflow boundaries

Validation

• npm test — 46 tests passed
• npm run lint
• npm run typecheck
• npm run check:prompts
• npm run validate:dogfood
• node scripts/check-codex-surface.mjs
• final llmdoc state: 0 impacted, 0 dirty, knowledge clean

The branch was rebased onto the latest origin/main before these commits were created.