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/doc-sync.md

@@ -6,22 +6,23 @@ description: Synchronize all pending documentation updates in a single commit
 
 Apply all pending documentation updates detected by doc-guardian hooks.
 
+## Skills to Load
+
+- skills/sync-workflow.md
+- skills/drift-detection.md
+
 ## Visual Output
 
-When executing this command, display the plugin header:
-
 ```
-┌──────────────────────────────────────────────────────────────────┐
-│  📝 DOC-GUARDIAN · Documentation Sync                            │
-└──────────────────────────────────────────────────────────────────┘
++------------------------------------------------------------------+
+|  DOC-GUARDIAN - Documentation Sync                               |
++------------------------------------------------------------------+
 ```
 
-Then proceed with the sync.
-
 ## Process
 
 1. **Review Pending Queue**
-   List all documentation drift detected during this session.
+   Execute `skills/sync-workflow.md` - read `.doc-guardian-queue`
 
 2. **Batch Updates**
    For each pending item:
@@ -29,48 +30,13 @@ Then proceed with the sync.
    - Apply the update
    - Track in change list
 
-3. **Update Types**
-
-   **Reference Fixes:**
-   - Renamed function/class → update all doc references
-   - Changed signature → update parameter documentation
-   - Removed item → remove or mark deprecated in docs
-
-   **Content Sync:**
-   - Version numbers (Python, Node, dependencies)
-   - Configuration keys/values
-   - File paths and directory structures
-   - Command examples and outputs
-
-   **Structural:**
-   - Add missing sections for new features
-   - Remove sections for deleted features
-   - Reorder to match current code organization
-
-4. **Commit Strategy**
+3. **Commit Strategy**
    - Stage all doc changes together
    - Single commit: `docs: sync documentation with code changes`
-   - Include summary of what was updated in commit body
+   - Include summary in commit body
 
-5. **Clear Queue**
-   After successful sync, clear the queue file:
-   ```bash
-   echo "# Doc Guardian Queue - cleared after sync on $(date +%Y-%m-%d)" > .doc-guardian-queue
-   ```
+4. **Clear Queue**
+   After successful sync, clear the queue file
 
-6. **Output**
-```
-## Documentation Sync Complete
-
-### Files Updated
-- README.md (3 changes)
-- CLAUDE.md (1 change)
-- src/api/README.md (2 changes)
-
-### Changes Applied
-- Updated function reference: calculate_total → compute_total
-- Updated Python version: 3.9 → 3.11
-- Added docstring to create_order()
-
-Committed: abc123f
-```
+5. **Output**
+   Use format from `skills/sync-workflow.md`