refactor: extract skills from commands across 8 plugins

Refactored commands to extract reusable skills following the
Commands → Skills separation pattern. Each command is now <50 lines
and references skill files for detailed knowledge.

Plugins refactored:
- claude-config-maintainer: 5 commands → 7 skills
- code-sentinel: 3 commands → 2 skills
- contract-validator: 5 commands → 6 skills
- data-platform: 10 commands → 6 skills
- doc-guardian: 5 commands → 6 skills (replaced nested dir)
- git-flow: 8 commands → 7 skills

Skills contain: workflows, validation rules, conventions,
reference data, tool documentation

Commands now contain: YAML frontmatter, agent assignment,
skills list, brief workflow steps, parameters

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

plugins/doc-guardian/commands/changelog-gen.md

@@ -6,116 +6,49 @@ description: Generate changelog from conventional commits in Keep-a-Changelog fo
 
 Generate a changelog entry from conventional commits.
 
+## Skills to Load
+
+- skills/changelog-format.md
+
 ## Visual Output
 
-When executing this command, display the plugin header:
-
 ```
-┌──────────────────────────────────────────────────────────────────┐
-│  📝 DOC-GUARDIAN · Changelog Generation                          │
-└──────────────────────────────────────────────────────────────────┘
++------------------------------------------------------------------+
+|  DOC-GUARDIAN - Changelog Generation                             |
++------------------------------------------------------------------+
 ```
 
-Then proceed with the generation.
-
 ## Process
 
 1. **Identify Commit Range**
-   - Default: commits since last tag
-   - Optional: specify range (e.g., `v1.0.0..HEAD`)
-   - Detect if this is first release (no previous tags)
+   Execute `skills/changelog-format.md` - detect range from tags
 
 2. **Parse Conventional Commits**
-   Extract from commit messages following the pattern:
-   ```
-   <type>(<scope>): <description>
-
-   [optional body]
-
-   [optional footer(s)]
-   ```
-
-   **Recognized Types:**
-   | Type | Changelog Section |
-   |------|------------------|
-   | `feat` | Added |
-   | `fix` | Fixed |
-   | `docs` | Documentation |
-   | `perf` | Performance |
-   | `refactor` | Changed |
-   | `style` | Changed |
-   | `test` | Testing |
-   | `build` | Build |
-   | `ci` | CI/CD |
-   | `chore` | Maintenance |
-   | `BREAKING CHANGE` | Breaking Changes |
+   Use pattern from skill: `<type>(<scope>): <description>`
 
 3. **Group by Type**
-   Organize commits into Keep-a-Changelog sections:
-   - Breaking Changes (if any `!` suffix or `BREAKING CHANGE` footer)
-   - Added (feat)
-   - Changed (refactor, style, perf)
-   - Deprecated
-   - Removed
-   - Fixed (fix)
-   - Security
+   Map to Keep-a-Changelog sections per skill
 
 4. **Format Entries**
-   For each commit:
-   - Extract scope (if present) as prefix
+   - Extract scope as bold prefix
    - Use description as entry text
-   - Link to commit hash if repository URL available
-   - Include PR/issue references from footer
+   - Link commit hashes if repo URL available
 
-5. **Output Format**
-```markdown
-## [Unreleased]
-
-### Breaking Changes
-- **scope**: Description of breaking change
-
-### Added
-- **scope**: New feature description
-- Another feature without scope
-
-### Changed
-- **scope**: Refactoring description
-
-### Fixed
-- **scope**: Bug fix description
-
-### Documentation
-- Updated README with new examples
-```
+5. **Output**
+   Use format from `skills/changelog-format.md`
 
 ## Options
 
 | Flag | Description | Default |
 |------|-------------|---------|
-| `--from <tag>` | Start from specific tag | Latest tag |
-| `--to <ref>` | End at specific ref | HEAD |
-| `--version <ver>` | Set version header | [Unreleased] |
-| `--include-merge` | Include merge commits | false |
-| `--group-by-scope` | Group by scope within sections | false |
+| `--from <tag>` | Start from tag | Latest tag |
+| `--to <ref>` | End at ref | HEAD |
+| `--version <ver>` | Version header | [Unreleased] |
+| `--include-merge` | Include merges | false |
+| `--group-by-scope` | Group by scope | false |
 
 ## Integration
 
-The generated output is designed to be copied directly into CHANGELOG.md:
+Output designed for direct copy to CHANGELOG.md:
 - Follows [Keep a Changelog](https://keepachangelog.com) format
 - Compatible with semantic versioning
-- Excludes non-user-facing commits (chore, ci, test by default)
-
-## Example Usage
-
-```
-/changelog-gen
-/changelog-gen --from v1.0.0 --version 1.1.0
-/changelog-gen --include-merge --group-by-scope
-```
-
-## Non-Conventional Commits
-
-Commits not following conventional format are:
-- Listed under "Other" section
-- Flagged for manual categorization
-- Skipped if `--strict` flag is used