chore: prepare v1.9.1 release

[Kirachon]

Summary

• prepare the coordinated v1.9.1 patch release
• align package, lockfile, MCP manifest, reviewer tool, and CI version contracts
• preserve the historical local v1.9.0 tag and all unrelated dirty artifacts

Local verification

• npm run build
• npm run ci:check:docs-version-reconciliation
• node --import tsx scripts/ci/check-version-literals.ts
• npm run ci:check:supported-distribution-pack-proof
• compatibilityRollbackEnvelope.test.ts
• git diff --check

Q3d/T1*/A*/M1-M3 remain governed by the existing CONDITIONAL_GO release posture and are not claimed as completed by this patch.

[github-actions]

Code Review Summary

• Risk: 5/5
• Classification: refactor
• Hotspots: src/mcp
• CI gate: PASS

Classified as refactor. Risk 5/5. 12 files changed (+23/-24). 3 deterministic findings. Hotspots: src/mcp.

Findings

• HIGH PRE002 (architecture) at config/ci/compatibility-rollback-envelope.json:1: Possible public API surface change detected
• MEDIUM PRE003 (infra) at config/ci/compatibility-rollback-envelope.json:1: Configuration or CI-related files changed
• INFO PRE005 (maintainability) at config/ci/compatibility-rollback-envelope.json:1: Hotspot paths detected