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/framework-migration/skills/react-modernization/SKILL.md

@@ -495,32 +495,3 @@ function List<T>({ items, renderItem }: ListProps<T>) {
 - [ ] Check for warnings in console
 - [ ] Performance testing
 ```
-
-## Resources
-
-- **references/breaking-changes.md**: Version-specific breaking changes
-- **references/codemods.md**: Codemod usage guide
-- **references/hooks-migration.md**: Comprehensive hooks patterns
-- **references/concurrent-features.md**: React 18 concurrent features
-- **assets/codemod-config.json**: Codemod configurations
-- **assets/migration-checklist.md**: Step-by-step checklist
-- **scripts/apply-codemods.sh**: Automated codemod script
-
-## Best Practices
-
-1. **Incremental Migration**: Don't migrate everything at once
-2. **Test Thoroughly**: Comprehensive testing at each step
-3. **Use Codemods**: Automate repetitive transformations
-4. **Start Simple**: Begin with leaf components
-5. **Leverage StrictMode**: Catch issues early
-6. **Monitor Performance**: Measure before and after
-7. **Document Changes**: Keep migration log
-
-## Common Pitfalls
-
-- Forgetting useEffect dependencies
-- Over-using useMemo/useCallback
-- Not handling cleanup in useEffect
-- Mixing class and functional patterns
-- Ignoring StrictMode warnings
-- Breaking change assumptions