issue: #42661
Add NotStopped() and IsWorking() methods to shardDelegator for better
state management and error handling.
Changes include:
- Add instance state checking methods with proper error messages
- Replace lifetime package calls with delegator instance methods
- Add comprehensive unit tests for state transitions and error cases
- Improve error reporting with channel name for better debugging
Signed-off-by: Wei Liu <wei.liu@zilliz.com>