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-dry.md

@@ -8,16 +8,12 @@ Analyze and preview refactoring opportunities without making changes.
 
 ## Visual Output
 
-When executing this command, display the plugin header:
-
 ```
-┌──────────────────────────────────────────────────────────────────┐
-│  🔒 CODE-SENTINEL · Refactor Preview                             │
-└──────────────────────────────────────────────────────────────────┘
++----------------------------------------------------------------------+
+|  CODE-SENTINEL - Refactor Preview                                    |
++----------------------------------------------------------------------+
 ```
 
-Then proceed with the analysis.
-
 ## Usage
 ```
 /refactor-dry <target> [--all]
@@ -26,44 +22,31 @@ Then proceed with the analysis.
 **Target:** File path, function name, or "." for current file
 **--all:** Show all opportunities, not just recommended
 
+## Skills to Load
+
+- skills/refactoring-patterns.md
+- skills/dry-run-workflow.md
+
 ## Process
 
-1. **Scan Target**
-   Analyze code for refactoring opportunities.
+1. **Scan Target** - Analyze code using patterns from skill
+2. **Score Opportunities** - Rate by Impact/Risk/Effort (see dry-run-workflow skill)
+3. **Output** - Group by recommended vs optional
 
-2. **Score Opportunities**
-   Each opportunity rated by:
-   - Impact (how much it improves code)
-   - Risk (likelihood of breaking something)
-   - Effort (complexity of the refactoring)
+## Output Format
 
-3. **Output**
 ```
-## Refactoring Opportunities: src/handlers.py
+## Refactoring Opportunities: <target>
 
 ### Recommended (High Impact, Low Risk)
+1. **pattern** at lines X-Y
+   - Impact: High | Risk: Low
+   - Run: `/refactor <target> --pattern=<pattern>`
 
-1. **extract-method** at lines 45-67
-   - Extract order validation logic
-   - Impact: High (reduces complexity from 12 to 4)
-   - Risk: Low (pure function, no side effects)
-   - Run: `/refactor src/handlers.py:45 --pattern=extract-method`
-
-2. **use-dataclass** for OrderInput class
-   - Convert to dataclass with validation
-   - Impact: Medium (reduces boilerplate)
-   - Risk: Low
-   - Run: `/refactor src/models.py:OrderInput --pattern=use-dataclass`
-
-### Optional (Consider Later)
-
-3. **use-fstring** at 12 locations
-   - Modernize string formatting
-   - Impact: Low (readability only)
-   - Risk: None
+### Optional
+- Lower priority items
 
 ### Summary
-- 2 recommended refactorings
-- 1 optional improvement
-- Estimated complexity reduction: 35%
+- X recommended, Y optional
+- Estimated complexity reduction: Z%
 ```