Add configurable submit buffer

README.md

@@ -17,11 +17,22 @@ if err := pool.Submit(func() { doWork() }); err != nil {
 
 The pool creates the minimum workers immediately and grows on demand up to the
 maximum. A channel-driven scheduler owns worker lifecycle and a FIFO task queue
-with fixed capacity `maxWorkers/2`; once all workers and queue slots are
-occupied, `Submit` waits for room. With `maxWorkers == 1`, the queue has zero
-capacity and submissions wait for a worker. A successful `Submit` means the
-scheduler accepted the task; it does not mean the task has started or finished.
-`Close` stops new submissions and waits for accepted tasks to finish.
+with fixed capacity `maxWorkers/2`. Submissions first pass through a separate
+FIFO ingress buffer, whose default capacity is 128. Configure it with
+`WithSubmitBuffer`; zero keeps the ingress unbuffered, and negative capacities
+are rejected:
+
+```go
+pool, err := worker.New(2, 8, worker.WithSubmitBuffer(1024))
+```
+
+The ingress buffer and scheduler queue are separate capacity limits. When the
+ingress buffer is full, `Submit` waits until the scheduler can accept more work
+or the pool begins closing. With `maxWorkers == 1`, the scheduler queue has zero
+capacity, though the ingress buffer can still hold its configured number of
+tasks. A successful `Submit` means the pool accepted the task; it does not mean
+the task has started or finished. `Close` stops new submissions and waits for
+all accepted tasks, including buffered submissions, to finish.
 
 After a task finishes, a worker exits immediately only when `total > min` and
 the number of *other* idle workers is greater than `min/2`. There is no idle