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/claude-config-maintainer/skills/optimization-patterns.md

@@ -0,0 +1,136 @@
+# CLAUDE.md Optimization Patterns
+
+This skill defines patterns for optimizing CLAUDE.md files.
+
+## Optimization Categories
+
+### Restructure
+- Reorder sections by importance (Quick Start near top)
+- Group related content together
+- Improve header hierarchy
+- Add navigation aids (TOC for long files)
+
+### Condense
+- Remove redundant explanations
+- Convert verbose text to bullet points
+- Eliminate duplicate content
+- Shorten overly detailed sections
+
+### Enhance
+- Add missing essential sections
+- **Add Pre-Change Protocol if missing (HIGH PRIORITY)**
+- Improve unclear instructions
+- Add helpful examples
+- Highlight critical rules
+
+### Format
+- Standardize header styles (no trailing colons)
+- Fix code block formatting (add language tags)
+- Align list formatting (consistent markers)
+- Improve table layouts
+
+## Scoring Criteria
+
+### Structure (25 points)
+- Logical section ordering
+- Clear header hierarchy
+- Easy navigation
+- Appropriate grouping
+
+### Clarity (25 points)
+- Clear instructions
+- Good examples
+- Unambiguous language
+- Appropriate detail level
+
+### Completeness (25 points)
+- Project overview present
+- Quick start commands documented
+- Critical rules highlighted
+- Key workflows covered
+- Pre-Change Protocol present (MANDATORY)
+
+### Conciseness (25 points)
+- No unnecessary repetition
+- Efficient information density
+- Appropriate length for project size
+- No generic filler content
+
+## Score Interpretation
+
+| Score | Rating | Action |
+|-------|--------|--------|
+| 90-100 | Excellent | Maintenance only |
+| 70-89 | Good | Minor improvements |
+| 50-69 | Needs Work | Optimization recommended |
+| Below 50 | Poor | Major restructuring needed |
+
+## Common Optimizations
+
+### Verbose to Concise
+```markdown
+# Before (34 lines)
+## Running Tests
+To run the tests, you first need to make sure you have all the
+dependencies installed. The dependencies are listed in requirements.txt.
+Once you have installed the dependencies, you can run the tests using
+pytest. Pytest will automatically discover all test files...
+
+# After (8 lines)
+## Running Tests
+```bash
+pip install -r requirements.txt  # Install dependencies
+pytest                           # Run all tests
+pytest -v                        # Verbose output
+pytest tests/unit/               # Run specific directory
+```
+```
+
+### Duplicate Removal
+- Keep first occurrence
+- Add cross-reference if needed: "See [Section Name] above"
+
+### Header Standardization
+```markdown
+# Before
+## Quick Start:
+## Architecture
+## Testing:
+
+# After
+## Quick Start
+## Architecture
+## Testing
+```
+
+### Code Block Enhancement
+```markdown
+# Before
+```
+npm install
+npm test
+```
+
+# After
+```bash
+npm install  # Install dependencies
+npm test     # Run test suite
+```
+```
+
+## Safety Features
+
+### Backup Creation
+- Always backup before changes
+- Store in `.claude/backups/CLAUDE.md.TIMESTAMP`
+- Easy restoration if needed
+
+### Preview Mode
+- Show all changes before applying
+- Use diff format for easy review
+- Allow approve/reject per change
+
+### Selective Application
+- Can apply individual changes
+- Skip specific optimizations
+- Iterative refinement supported