feat(worker)!: promote to v1.0.0 — add Len() to Provider, bump deps to v1

Add Len() int to Provider interface; returns current queue depth for
observability and test assertions. Bump launcher and logz to v1.0.1.
Go directive bumped to 1.26. API committed as stable.

worker.go

@@ -16,6 +16,8 @@ type Task func(ctx context.Context) error
 type Provider interface {
 	// Dispatch queues a task. Returns false if the queue is full (backpressure).
 	Dispatch(task Task) bool
+	// Len returns the current number of tasks waiting in the queue.
+	Len() int
 }
 
 // Component adds lifecycle management to Provider.
@@ -103,6 +105,8 @@ func (w *workerComponent) OnStop() error {
 	return nil
 }
 
+func (w *workerComponent) Len() int { return len(w.taskQueue) }
+
 func (w *workerComponent) Dispatch(task Task) bool {
 	select {
 	case w.taskQueue <- task: