feat(plugins): implement Sprint 4 commands (#241-#258)

Sprint 4 - Plugin Commands implementation adding 18 new user-facing
commands across 8 plugins as part of V5.2.0 Plugin Enhancements.

**projman:**
- #241: /sprint-diagram - Mermaid visualization of sprint issues

**pr-review:**
- #242: Confidence threshold config (PR_REVIEW_CONFIDENCE_THRESHOLD)
- #243: /pr-diff - Formatted diff with inline review comments

**data-platform:**
- #244: /data-quality - DataFrame quality checks (nulls, duplicates, outliers)
- #245: /lineage-viz - dbt lineage as Mermaid diagrams
- #246: /dbt-test - Formatted dbt test runner

**viz-platform:**
- #247: /chart-export - Export charts to PNG/SVG/PDF via kaleido
- #248: /accessibility-check - Color blind validation (WCAG contrast)
- #249: /breakpoints - Responsive layout configuration

**contract-validator:**
- #250: /dependency-graph - Plugin dependency visualization

**doc-guardian:**
- #251: /changelog-gen - Generate changelog from conventional commits
- #252: /doc-coverage - Documentation coverage metrics
- #253: /stale-docs - Flag outdated documentation

**claude-config-maintainer:**
- #254: /config-diff - Track CLAUDE.md changes over time
- #255: /config-lint - 31 lint rules for CLAUDE.md best practices

**cmdb-assistant:**
- #256: /cmdb-topology - Infrastructure topology diagrams
- #257: /change-audit - NetBox audit trail queries
- #258: /ip-conflicts - Detect IP conflicts and overlaps

Closes #241, #242, #243, #244, #245, #246, #247, #248, #249,
#250, #251, #252, #253, #254, #255, #256, #257, #258

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

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

@@ -0,0 +1,109 @@
+---
+description: Generate changelog from conventional commits in Keep-a-Changelog format
+---
+
+# Changelog Generation
+
+Generate a changelog entry from conventional commits.
+
+## 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)
+
+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 |
+
+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
+
+4. **Format Entries**
+   For each commit:
+   - Extract scope (if present) as prefix
+   - Use description as entry text
+   - Link to commit hash if repository URL available
+   - Include PR/issue references from footer
+
+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
+```
+
+## 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 |
+
+## Integration
+
+The generated output is designed to be copied directly into 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