handleTaskCompleted and handlePhaseAllTasksDone both bailed early when
initiative had no branch, silently skipping phase status transitions.
Also, merge failures would skip the phase completion check entirely.
- Decouple phase completion check from branch existence
- Wrap merge in try/catch so phase check runs even if merge fails
- Route updateTaskStatus through dispatchManager.completeTask when
completing, so the task:completed event fires for orchestration
14d09b16df