feat(m1): scaffold tsmm package (T1.1)

- pyproject.toml (src-layout, deps per plan)
- src/tsmm/{data,model,train,eval} skeletons
- tests/test_smoke.py (RED->GREEN: importable + subpackages)
- configs/, scripts/, data/, checkpoints/ + .gitignore
- project venv (.venv) for reproducible env (M1 deps only; CUDA torch @ M2)

Verifications: import tsmm OK; pytest tests/ 3 passed.

.gitignore

@@ -4,6 +4,16 @@
 node_modules/
 jspm_packages/
 
+# Python
+.venv/
+venv/
+env/
+__pycache__/
+*.py[cod]
+*.egg-info/
+.pytest_cache/
+.ipynb_checkpoints/
+
 # ─────────────────────────────────────────────────────────────
 # Build output & caches
 # ─────────────────────────────────────────────────────────────