Clean up docs/ folder by removing build artifacts and redundant files

- Removed docs/_build/ directory (Sphinx build artifacts)
- Removed auto_examples/ generated files: *.zip, *.codeobj.json, *.py.md5
- Removed orphaned notebook files: decode_by_weighted_randinit.ipynb, simulate_data.ipynb
- Removed tutorial/Makefile and tutorial/tools/ (obsolete conversion scripts)
- Removed tutorial/timecorr_notebook.rst (generated file)
- Removed individual function RST files (redundant with api.rst)
- Removed make.bat (Windows batch file)
- Removed sg_execution_times.rst (generated file)

All removed files are either build artifacts that can be regenerated
or redundant documentation files that are no longer needed.

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

Co-Authored-By: Claude <noreply@anthropic.com>

Author: jeremymanning