Retire the legacy capacity client wrapper

docs/internal/capacity.md

@@ -68,9 +68,8 @@ Preparation and validation never hold an active permit.
 
 The manager's `Acquire` operation owns that active-permit acquisition and
 returns an idempotent release function. The coordinator uses it around
-individual attempts. The earlier one-shot wrapper still delegates to the same
-operation for focused internal callers and tests, but engine assembly no
-longer uses it. There is one queue and one active limit per limited backend pool.
+individual attempts. There is one queue and one active limit per limited backend
+pool.
 
 When all active permits are occupied, calls join a mutex-protected FIFO waiter
 list. Releasing a permit transfers it directly to the oldest remaining waiter
@@ -121,7 +120,7 @@ validation, bounded admission, idempotent release, context handling, and
 unlimited admission. The
 [client tests](../../internal/capacity/client_test.go) own peak enforcement,
 FIFO transfer, canceled-waiter removal, grant/cancel races, independent pools,
-unlimited calls, passthrough behavior, and panic release.
+unlimited calls, and panic release using test-only one-shot calls.
 
 The [runner tests](../../internal/usecase/runner_test.go) own ordinary early
 admission, lease lifetime, failure release, and shared initial/repair