Missing dependency validation allows non-existent task IDs to be added as dependencies, causing tasks to be permanently blocked.

If input.dependsOn contains task IDs that don't exist in the queue, the new task will never become runnable because nextRunnable() checks if all dependencies are in the doneIds set. Non-existent IDs will never be in that set.

This creates a silent deadlock where tasks appear pending but can never run, and isDrained() will return true even though work is incomplete.

enqueue(input: EnqueueInput): QueuedTask {
  // Validate dependencies exist
  if (input.dependsOn) {
    const existingIds = new Set(this.tasks.map(t => t.id));
    const invalid = input.dependsOn.filter(id => !existingIds.has(id));
    if (invalid.length > 0) {
      throw new Error(`Invalid dependencies: ${invalid.join(', ')}`);
    }
  }
  
  const task: QueuedTask = {
    // ... rest of implementation
  };
}

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SNAKE CASE NOOOOO

WAT

are we preventing circular deps? dependsOn forming a cycle (A→B→A) or pointing at a non-existent id

what about failed? does the queue just stop?

enqueuedBy is free-form and tasks can enqueue tasks. Without a depth or count bound, a misbehaving task type can grow the queue unboundedly