add .gitignore — skip __pycache__ and the huge raw site/*/traces.json files (lives in bucket instead)

.gitignore

@@ -0,0 +1,14 @@
+# Local Python bytecode
+__pycache__/
+*.pyc
+
+# Raw per-sweep trace files — huge (hundreds of MB), live in the bucket instead.
+# build_data.py writes these locally; we sync site/*/traces.json to the bucket
+# via `hf sync`, never commit them (would blow past the 1 GB LFS cap on Spaces).
+site/*/traces.json
+site/*/traces.json.gz
+
+# Editor leftovers
+.DS_Store
+.idea/
+.vscode/