Release Workflow: Post-release changelog validation missing

[ashleyshaw]

Issue

After release agent updates CHANGELOG.md and creates a new [Unreleased] section (per issue #586), there's no validation that the new structure is schema-valid.

Impact

• Silent drift between intended and actual changelog format
• Next PR finds an invalid changelog → validation fails
• Breaks changelog validation gate for next development cycle

Root Cause

.github/workflows/release.yml validates CHANGELOG before release (line 105–108) but not after. After agent modifies the file, there's no re-validation.

Expected Behavior

After release agent completes (or specifically after changelog update), add:

release:
  # ... existing steps ...
  
  - name: Validate post-release changelog
    if: inputs.dry_run == false
    run: |
      node scripts/validation/validate-changelog.cjs CHANGELOG.md
      node scripts/agents/includes/changelogUtils.cjs --validate CHANGELOG.md
      node scripts/agents/includes/changelogUtils.cjs --unreleased CHANGELOG.md

This ensures the new Unreleased section is valid before committing.

References

• Related audit: .github/reports/audits/RELEASE_PROCESS_AUDIT_v0_5_0.md (Issue 3.1)
• Workflow: .github/workflows/release.yml
• Validation scripts: scripts/validation/validate-changelog.cjs, scripts/agents/includes/changelogUtils.cjs

[linear-code]

LS-785