fix: replace python3 with py/jq throughout scripts and docs

Windows Store python3 stub returns exit 49 instead of running Python.
Replace with: py (Windows launcher) for actual Python code, jq for
simple JSON extraction. Reorder fallback loops to try py first.
Add Bash(py:*) to settings.local.json allowlist.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/DATABASE_FIRST_PROTOCOL.md

@@ -232,7 +232,7 @@ curl http://172.16.3.30:8001/health
 # Check total contexts
 curl -H "Authorization: Bearer $JWT" \
   http://172.16.3.30:8001/api/conversation-contexts | \
-  python -c "import sys,json; print(f'Total: {json.load(sys.stdin)[\"total\"]}')"
+  jq -r '.total'
 
 # Try different search term
 # Instead of: search_term=dataforth%20DOS