fix: replace jq dependency with python3 in ralph-wiggum stop hook

[clowerweb]

Summary

• Replace all 3 jq calls in stop-hook.sh with python3 equivalents
• Add Requirements section to README.md documenting the python3 dependency

The ralph-wiggum stop hook uses jq for JSON parsing, but jq is not available by default on Windows/Git Bash, causing command not found errors. Python 3 is far more universally available and handles JSON natively via json module.

Replacements:

1. Line 58: jq -r '.transcript_path' → python3 -c "import sys,json; print(json.load(sys.stdin).get('transcript_path',''))"
2. Lines 90-95: Complex .message.content extraction → equivalent Python with error handling
3. Lines 167-174: jq -n --arg JSON construction → python3 -c "import json; print(json.dumps(...))" with proper escaping via sys.argv

Test plan

• Verify stop hook correctly extracts transcript path from hook input JSON
• Verify stop hook correctly parses assistant message text from JSONL transcript
• Verify stop hook outputs valid JSON with decision/reason/systemMessage fields
• Verify ralph-loop iteration cycle works end-to-end (start → iterate → complete)
• Test on Windows/Git Bash where jq is not installed

Fixes #14817

🤖 Generated with Claude Code

[pypetey]

On Windows frequently python is called via python instead of python3 so a lot of people would still have issues.