docs: Add comprehensive debugging guide with depyler --trace/--explain and renacer workflows

Add DEBUGGING.md (600+ lines) covering complete debugging workflows:

- Phase 1: Transpilation debugging with depyler --trace and --explain flags
- Phase 2: Compile-time analysis with systematic error investigation
- Phase 3: Runtime tracing with renacer syscall and function profiling

Key sections:
- Variable scope debugging examples
- Type inference debugging workflows
- argparse → clap transformation analysis
- Complete end-to-end debugging example (Vec<String> Display issue)
- Reproducibility best practices with trace output

Integration:
- Renacer for syscall tracing with source correlation
- Function profiling and flamegraph generation
- I/O bottleneck detection
- Complete debugging cheatsheet

Updated README.md to reference DEBUGGING.md in Quick Start and Documentation sections.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: noahgift