refactor: Simplify Event System — replace overhead events with direct calls (Phase 1)

[dean0x]

Epic: #87 — Architectural Simplification v0.6.0

Goal

Remove ~22 overhead events, replace with direct calls. Keep events only for genuine fan-out (terminal-state handlers) and command triggers.

Sub-tasks

1a. Replace Query Events with Direct Calls

Problem: TaskManager uses eventBus.request(TaskStatusQuery) → QueryHandler → taskRepo.findById(). This adds ~1ms latency per query and exists only for architectural purity.

Change: Inject TaskRepository and OutputCapture into TaskManagerService. Replace request() calls with direct repository calls.

Files:

• src/services/task-manager.ts — Add taskRepo: TaskRepository and outputCapture: OutputCapture to constructor. Replace request(TaskStatusQuery) with taskRepo.findById(). Replace request(TaskLogsQuery) with outputCapture.getOutput().
• src/bootstrap.ts — Pass taskRepository and outputCapture to TaskManagerService constructor.
• src/core/events/events.ts — Remove TaskStatusQuery, TaskStatusResponse, TaskLogsQuery, TaskLogsResponse event types.
• src/services/handlers/query-handler.ts — Remove entirely (all functionality moved to direct calls).
• src/services/handler-setup.ts — Remove QueryHandler from standard handlers list.
• Tests: Remove query-handler tests, update task-manager tests.

Also: Replace eventBus.request(NextTaskQuery) in WorkerHandler with direct queue.dequeue() call.

• src/services/handlers/worker-handler.ts — Inject TaskQueue, call queue.dequeue() directly.
• src/core/events/events.ts — Remove NextTaskQuery event type.
• src/services/handlers/queue-handler.ts — Remove NextTaskQuery subscription and handler.

1b. Linearize the Trigger Chain

Problem: TaskDelegated → PersistenceHandler.save() → emit TaskPersisted → QueueHandler.enqueue() → emit TaskQueued → WorkerHandler.processNextTask(). This is a strictly sequential pipeline pretending to be event-driven.

Change: TaskManager.delegate() calls taskRepo.save() directly, then calls queue.enqueue() (via a new method or direct call), then triggers worker processing. The TaskDelegated event is still emitted for fan-out subscribers (DependencyHandler needs it).

Files:

• src/services/task-manager.ts — After emitting TaskDelegated, call taskRepo.save(task) directly, then queue.enqueue(task) (if not blocked by dependencies).
• src/services/handlers/persistence-handler.ts — Remove TaskDelegated subscription (TaskManager now saves directly). Keep terminal-state subscriptions (TaskStarted, TaskCompleted, TaskFailed, TaskCancelled, TaskTimeout).
• src/services/handlers/queue-handler.ts — Remove TaskPersisted subscription. Add direct enqueueIfReady(task) method callable by TaskManager.
• src/core/events/events.ts — Remove TaskPersisted event type.

Keep: TaskDelegated event (DependencyHandler subscribes), TaskQueued event (WorkerHandler subscribes — or make this a direct call too in 1c).

1c. Remove Informational-Only Events

Problem: OutputCaptured, WorkerSpawned, RecoveryStarted, RecoveryCompleted, SystemResourcesUpdated are consumed only for debug logging or advisory metrics.

Change: Replace with direct logger calls at the point of action. Remove event definitions and subscriptions.

Files:

• src/core/events/events.ts — Remove the 5 event types listed above.
• src/implementations/event-driven-worker-pool.ts — Remove WorkerSpawned emission (already logged locally).
• src/implementations/output-capture.ts — Remove OutputCaptured emission.
• src/services/recovery-manager.ts — Remove RecoveryStarted/RecoveryCompleted emissions (already logged).
• src/services/handlers/output-handler.ts — Remove entirely (only consumed OutputCaptured for debug logging).
• src/services/autoscaling-manager.ts — Remove SystemResourcesUpdated subscription. If AutoscalingManager is advisory-only with no actionable behavior, consider removing it entirely.

1d. Resolve waitForCheckpoint Race Condition

Problem: DependencyHandler and CheckpointHandler both subscribe to TaskCompleted. DependencyHandler needs the checkpoint that CheckpointHandler creates, so it races with a subscription + DB lookup (lines 444-494 in dependency-handler.ts).

Change: With the hybrid model, make checkpoint creation explicit in the completion path. The completion fan-out calls CheckpointHandler.createCheckpoint() first, then DependencyHandler.resolveDependencies(). The race condition disappears.

Files:

• src/services/handlers/dependency-handler.ts — Remove waitForCheckpoint() method and race logic. Accept checkpoint as a parameter or query it after guaranteed creation.

Files Changed

Modified

• src/services/task-manager.ts
• src/core/events/events.ts
• src/services/handlers/worker-handler.ts
• src/services/handlers/queue-handler.ts
• src/services/handlers/persistence-handler.ts
• src/services/handlers/dependency-handler.ts
• src/services/handler-setup.ts
• src/bootstrap.ts
• src/implementations/event-driven-worker-pool.ts
• src/implementations/output-capture.ts
• src/implementations/resource-monitor.ts
• src/services/recovery-manager.ts

Removed

• src/services/handlers/query-handler.ts — Replaced by direct repo calls
• src/services/handlers/output-handler.ts — Only consumed debug event
• src/services/autoscaling-manager.ts — Advisory-only, no actionable behavior
• tests/unit/services/handlers/query-handler.test.ts
• tests/unit/services/handlers/output-handler.test.ts

Risk

Medium — touches core orchestration and task delegation flow. Sub-steps (1a → 1b → 1c → 1d) can be validated incrementally.

Verification

• npm run build — clean compilation
• npx biome check src/ tests/ — no lint issues
• All test groups pass: core, handlers, services, repositories, adapters, CLI, integration
• Event audit: grep -r "emit\|subscribe" src/ shows only ~15 retained events