chore: gitignore .superset directory

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jla415

.gitignore

@@ -119,3 +119,6 @@ bd_test
 # Gas Town (added by gt)
 .logs/
 .beads/
+
+# Superset
+.superset/