Add code review skill

skills/code/review.md

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+# Skill: Code Review
+
+## Description
+Performs a focused code review on a pull request or diff, checking for security, performance, architecture, testing, and style issues.
+
+## Input
+- **diff**: The code diff to review (required)
+- **context**: Additional context about the changes (optional)
+- **focus_areas**: Specific areas to focus on (optional)
+
+## Checklist
+1. **Security**: SQL injection, XSS, auth bypass, secrets exposure
+2. **Performance**: N+1 queries, memory leaks, blocking operations
+3. **Architecture**: SOLID violations, coupling, abstraction leaks
+4. **Testing**: Coverage gaps, edge cases, mocking issues
+5. **Style**: Naming conventions, formatting, documentation
+
+## Output Format
+```json
+{
+  "severity": "pass|warn|fail",
+  "issues": [
+    {
+      "line": 42,
+      "file": "path/to/file.js",
+      "type": "security|performance|architecture|testing|style",
+      "severity": "critical|major|minor",
+      "description": "Issue description",
+      "suggestion": "How to fix"
+    }
+  ],
+  "summary": "Brief overall assessment",
+  "score": 85
+}
+```
+
+## Token Budget
+- Max input: 4000 tokens
+- Max output: 800 tokens
+
+## Model
+- Recommended: sonnet (code analysis requires reasoning)