Handle parameterized base64 image data URLs

- accept `data:image/...;...;base64,...` headers while still rejecting invalid formats
- add `imageMime` tests for mime params, non-base64 URLs, and missing mime types
- fork branch-generation prompt effect at call site in `ProviderCommandReactor`
70857ce299Julius Marminge committed on 3/2/2026, 4:06:21 AM· committed by Julius Marmingeparent5e0ec38
3 files changedLine totals unavailable