chore: add Gas Town directories to gitignore

Added .runtime/, .claude/, and .logs/ to gitignore for Gas Town polecat workspace.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -1,3 +1,8 @@
 result
 thoughts
 .beads
+
+# Gas Town (added by gt)
+.runtime/
+.claude/
+.logs/