chore: trim requirements.txt to only ML pipeline deps, fix venv path, add .venv to gitignore

- requirements.txt: 230 → 11 top-level packages (removed transitive deps, CUDA/JAX/PyTorch/HuggingFace/Jupyter noise)
- CLAUDE.md: update venv setup to point at repo-root .venv
- .gitignore: add .venv/ and venv/ entries
- Memory: record venv location to avoid duplicate creation

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

.gitignore

@@ -9,6 +9,8 @@ dist/
 build/
 coverage/
 *.tsbuildinfo
+.venv/
+venv/
 
 .DS_Store