feat: add CONTRIBUTING.md to community-health and sync

[wcmchenry3-stack]

Context

No CONTRIBUTING.md exists in any org repo. Contributors (including Claude Code agents) have no documented source of truth for branch naming, commit format, PR process, or how release-please auto-generates releases. GitHub surfaces a "missing Contributing" warning in the community standards checklist.

Implementation

1. Create community-health/CONTRIBUTING.md

Must cover:

Branch naming conventions

• feat/<slug> — new features
• fix/<slug> — bug fixes
• chore/<slug> — maintenance
• docs/<slug> — documentation only

Conventional Commits (enforced by commitlint.yml)

• PR titles must match <type>[!]: <subject>
• Type list: feat, fix, perf, docs, chore, ci, test, style, refactor, build
• ! suffix or BREAKING CHANGE: footer triggers major bump (or minor in pre-1.0)
• Repos use squash-merge — PR title becomes the commit on main

PR process

• Open draft PRs targeting dev (not main)
• main receives PRs only from dev or from release-please Release PRs
• All CI checks must pass before merge
• At least one approval required (CODEOWNERS enforces this)

Release process

• Merge feat/fix PRs to main (via dev)
• release-please automatically opens a Release PR with updated CHANGELOG and bumped version
• Merge the Release PR to publish a GitHub Release and create a git tag

First-time setup (for human contributors)

• Prerequisites, clone, install steps (generic, project-specific READMEs take precedence)

2. Add to sync-community-health.yml FILE_MAP

- src: community-health/CONTRIBUTING.md
  dst: CONTRIBUTING.md

Acceptance Criteria

• community-health/CONTRIBUTING.md created covering all sections above
• Conventional Commits table matches the commitlint config enforced in commitlint.yml
• Branch naming matches the conventions documented in CLAUDE.md global standards
• File passes markdownlint
• FILE_MAP entry added to sync-community-health.yml
• GitHub community standards checklist shows Contributing as complete

Dependencies

None — can be worked in parallel with all other Phase 2 issues.
Issue #84 (make repo private) is blocked until this issue is complete.

Part of Epic

#77

[wcmchenry3-stack]

Implemented in PR #99 and #106 (both merged). Closing.