fix(skills): remove phantom resource references and fix CoC links (#447)

Remove references to non-existent resource files (references/, assets/,
scripts/, examples/) from 115 skill SKILL.md files. These sections
pointed to directories and files that were never created, causing
confusion when users install skills.

Also fix broken Code of Conduct links in issue templates to use
absolute GitHub URLs instead of relative paths that 404.

plugins/python-development/skills/python-testing-patterns/SKILL.md

@@ -1026,25 +1026,3 @@ exclude_lines = [
     "raise NotImplementedError",
 ]
 ```
-
-## Resources
-
-- **pytest documentation**: https://docs.pytest.org/
-- **unittest.mock**: https://docs.python.org/3/library/unittest.mock.html
-- **hypothesis**: Property-based testing
-- **pytest-asyncio**: Testing async code
-- **pytest-cov**: Coverage reporting
-- **pytest-mock**: pytest wrapper for mock
-
-## Best Practices Summary
-
-1. **Write tests first** (TDD) or alongside code
-2. **One assertion per test** when possible
-3. **Use descriptive test names** that explain behavior
-4. **Keep tests independent** and isolated
-5. **Use fixtures** for setup and teardown
-6. **Mock external dependencies** appropriately
-7. **Parametrize tests** to reduce duplication
-8. **Test edge cases** and error conditions
-9. **Measure coverage** but focus on quality
-10. **Run tests in CI/CD** on every commit