* fix: handle batch events format in manage_calendar tool
Models like deepseek-v4-flash emit batch events array instead of individual create_event calls. The tool defaulted to list_events (no action key), so events were never created despite the model confirming success.
- Add batch normalization in do_manage_calendar
- Map start/end objects to flat dtstart/dtend strings
- Add tests for both object and flat string formats
* fix: surface partial batch failures in manage_calendar
Partial failures were silently dropped - batches with mixed success/failure would report only created count with no error visibility.
- Return non-zero exit code for any failures
- Surface both created and failed counts in response
- Include first error message for debugging
- Add test for partial failure case
* chore: strip trailing whitespace in batch normalization block
* chore: strip whitespace-only blank lines in batch events test
Srinesh R