chore: start transition layout — python into version-python/, scaffold version-rust/

- git mv of all existing files into version-python/ (history preserved)
- version-rust/: minimal cargo scaffold (edition 2024), no deps yet
- root AGENTS.md documents the transition rules and artifact/schema contract
- main is untouched; the python layout there stays as-is

version-python/.gitignore

@@ -0,0 +1,24 @@
+# Python
+__pycache__/
+*.pyc
+.venv/
+*.egg-info/
+
+# Run outputs (if OUT_DIR points into the repo)
+thread/
+downloads/
+export.json
+export.html
+state.json
+state.json.tmp
+failed_urls.txt
+manifest.jsonl
+*.log
+
+# Never commit credentials
+*.token
+.env
+
+# Algolia credentials (search-only key, still never commit)
+algolia.json
+gwshop_raw.json