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/code-sentinel/commands/refactor.md

@@ -8,16 +8,12 @@ Apply refactoring transformations to specified code.
 
 ## Visual Output
 
-When executing this command, display the plugin header:
-
 ```
-┌──────────────────────────────────────────────────────────────────┐
-│  🔒 CODE-SENTINEL · Refactor                                     │
-└──────────────────────────────────────────────────────────────────┘
++----------------------------------------------------------------------+
+|  CODE-SENTINEL - Refactor                                            |
++----------------------------------------------------------------------+
 ```
 
-Then proceed with the refactoring workflow.
-
 ## Usage
 ```
 /refactor <target> [--pattern=<pattern>]
@@ -26,68 +22,31 @@ Then proceed with the refactoring workflow.
 **Target:** File path, function name, or "." for current context
 **Pattern:** Specific refactoring pattern (optional)
 
-## Available Patterns
+## Skills to Load
 
-### Structure
-| Pattern | Description |
-|---------|-------------|
-| `extract-method` | Extract code block into named function |
-| `extract-class` | Move related methods to new class |
-| `inline` | Inline trivial function/variable |
-| `rename` | Rename with all references updated |
-| `move` | Move function/class to different module |
-
-### Simplification
-| Pattern | Description |
-|---------|-------------|
-| `simplify-conditional` | Flatten nested if/else |
-| `remove-dead-code` | Delete unreachable code |
-| `consolidate-duplicate` | Merge duplicate code blocks |
-| `decompose-conditional` | Break complex conditions into named parts |
-
-### Modernization
-| Pattern | Description |
-|---------|-------------|
-| `use-comprehension` | Convert loops to list/dict comprehensions |
-| `use-pathlib` | Replace os.path with pathlib |
-| `use-fstring` | Convert .format() to f-strings |
-| `use-typing` | Add type hints |
-| `use-dataclass` | Convert class to dataclass |
+- skills/refactoring-patterns.md
 
 ## Process
 
-1. **Analyze Target**
-   - Parse code structure
-   - Identify refactoring opportunities
-   - Check for side effects and dependencies
+1. **Analyze Target** - Parse code, identify opportunities from skill, check dependencies
+2. **Propose Changes** - Show before/after diff, explain improvement, list affected files
+3. **Apply (with confirmation)** - Make changes, update references, run tests
 
-2. **Propose Changes**
-   - Show before/after diff
-   - Explain the improvement
-   - List affected files/references
+## Output Format
 
-3. **Apply (with confirmation)**
-   - Make changes
-   - Update all references
-   - Run existing tests if available
-
-4. **Output**
 ```
-## Refactoring: extract-method
+## Refactoring: <pattern>
 
 ### Target
-src/handlers.py:create_order (lines 45-89)
+<file>:<function> (lines X-Y)
 
 ### Changes
-- Extracted validation logic → validate_order_input()
-- Extracted pricing logic → calculate_order_total()
-- Original function now 15 lines (was 44)
+- Change description
 
 ### Files Modified
-- src/handlers.py
-- tests/test_handlers.py (updated calls)
+- file1.py
 
 ### Metrics
-- Cyclomatic complexity: 12 → 4
-- Function length: 44 → 15 lines
+- Cyclomatic complexity: X -> Y
+- Function length: X -> Y lines
 ```