chore(checkpoint): record governance closure and gate3 success evidence

[sriinnu]

Summary:

• update governance checkpoint and handover docs to reflect completed guardrails setup
• record compliant governance recapture snapshot (contains_NPM_TOKEN=true, npm_publish_environment_present=true, branch protection enabled)
• record successful Gate 3 dry-run workflow run 22670960699 and clean-tree guardrails pass

Validation run:

• npm run release:proxy:guardrails -- --batch-date 2026-03-03 --package-selector @commandrelay/proxy-*

Evidence:

• https://github.com/sriinnu/command-relay/actions/runs/22670960699