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-performance-optimization/SKILL.md

@@ -849,26 +849,3 @@ def test_map_function(benchmark):
 - Ignoring algorithmic complexity
 - Over-optimizing rare code paths
 - Not considering memory usage
-
-## Resources
-
-- **cProfile**: Built-in CPU profiler
-- **memory_profiler**: Memory usage profiling
-- **line_profiler**: Line-by-line profiling
-- **py-spy**: Sampling profiler for production
-- **NumPy**: High-performance numerical computing
-- **Cython**: Compile Python to C
-- **PyPy**: Alternative Python interpreter with JIT
-
-## Performance Checklist
-
-- [ ] Profiled code to identify bottlenecks
-- [ ] Used appropriate data structures
-- [ ] Implemented caching where beneficial
-- [ ] Optimized database queries
-- [ ] Used generators for large datasets
-- [ ] Considered multiprocessing for CPU-bound tasks
-- [ ] Used async I/O for I/O-bound tasks
-- [ ] Minimized function call overhead in hot loops
-- [ ] Checked for memory leaks
-- [ ] Benchmarked before and after optimization