Integrate testing-anti-patterns into test-driven-development

- Moved testing-anti-patterns to test-driven-development/testing-anti-patterns.md
- Added reference in TDD skill for progressive disclosure
- Updated README to reflect consolidation
- Removed standalone skill (now a supporting reference)

skills/test-driven-development/SKILL.md

@@ -354,6 +354,13 @@ Bug found? Write failing test reproducing it. Follow TDD cycle. Test proves fix
 
 Never fix bugs without a test.
 
+## Testing Anti-Patterns
+
+When adding mocks or test utilities, read @testing-anti-patterns.md to avoid common pitfalls:
+- Testing mock behavior instead of real behavior
+- Adding test-only methods to production classes
+- Mocking without understanding dependencies
+
 ## Final Rule
 
 ```

skills/test-driven-development/testing-anti-patterns.md

@@ -1,10 +1,7 @@
----
-name: testing-anti-patterns
-description: Use when writing or changing tests, adding mocks, or tempted to add test-only methods to production code - prevents testing mock behavior, production pollution with test-only methods, and mocking without understanding dependencies
----
-
 # Testing Anti-Patterns
 
+**Load this reference when:** writing or changing tests, adding mocks, or tempted to add test-only methods to production code.
+
 ## Overview
 
 Tests must verify real behavior, not mock behavior. Mocks are a means to isolate, not the thing being tested.