Remove tracked junk and tighten gitignore

Drop the accidental regression_test_bundle.json dump and a committed __pycache__ bytecode file. Ignore ruff/build caches and future root regression dumps.

Author: fraware

.gitignore

@@ -39,14 +39,19 @@ __pycache__/
 *.egg-info/
 .mypy_cache/
 .pytest_cache/
+.ruff_cache/
 .venv/
 venv/
+build/
 
 # Local package build trees (python -m build)
 extracted/python/dist/
 extracted/python/ds_guard-*/
 extracted/python/*.egg-info/
 
+# Accidental regression-test dump at repo root (tests write to temp files)
+regression_test_bundle.json
+
 # -----------------------
 # Rust
 # -----------------------