test(taskctl): add edge case tests for Pulse tick concurrency and crash recovery

[randomm]

Context

Code review of feature/taskctl-pipeline noted that Pulse tests cover basic scheduling and staging but are missing edge cases for the more complex failure scenarios.

Missing test coverage

Tick concurrency

• What happens if a tick takes > 10 seconds (the overlap guard)? Verify the tick is skipped, not queued
• What if processAdversarialVerdicts throws mid-loop? Does the lock clean up?

Lock file corruption

• Lock file exists with non-numeric content → readLockPid returns null correctly
• Lock file exists with PID of dead process → treated as zombie correctly in resume

Session resurrection edge cases

• Task in in_progress with worktree that no longer exists → resurrection handles missing worktree gracefully
• Task in adversarial-running with dead session → 60-min timeout transitions to reviewing

Completion edge cases

• Job with mix of closed + failed tasks → completion check correctly waits (not all closed)
• Job with zero tasks → completion fires immediately

Acceptance criteria

• At least 6 new meaningful tests covering the above scenarios
• bun test test/tasks/pulse.test.ts passes with 0 failures
• bun run typecheck passes with 0 errors