ci(gallery): diff each PR's touched gallery states against its merge-base - #18205

Bugbot Analysis Progress (1m 4s elapsed)

✅ Gathered PR context (29s)
✅ Completed bug detection (35s)
✅ Posted analysis results (1s)

Final Result: Bugbot completed review - no issues found. 4 previously reported issues remain unresolved.

Request ID: 9a59c6ad-bcfc-4ff0-bd19-a0de06c34514