Correct the stop timeout comments on the archive writers

The comments on the engine's stop and on the timeout test gave false
reasons for leaving archive writers open when the stop budget runs
out. Closing them would wait for any write in progress, and a worker
still running would then open new writers that nothing closes, so
closing gains nothing over a kill.

Model: opus-5-5

internal/delivery/engine.go

@@ -368,9 +368,9 @@ func (e *Engine) start() {
 // writer for long by then: the archive sweeper stops before the
 // engine, and deleting a webhook only closes one. If the pool did
 // not drain in time, the writers are left open, as a kill would
-// leave them: a worker still running may be mid-write, and
+// leave them. Closing them would wait for any write in progress,
-// closing its writer would wait on that write and then fail the
+// and a worker still running would then open new writers that
-// next delivery the worker archives.
+// nothing closes, so it gains nothing over a kill.
 func (e *Engine) stop(ctx context.Context) error {
 	e.log.Info("delivery engine stopping")
 

internal/delivery/engine_lifecycle_test.go

@@ -327,10 +327,10 @@ func TestEngine_StopHookClosesArchives(t *testing.T) {
 }
 
 // TestEngine_StopHookTimeoutLeavesArchivesOpen covers a stop whose
-// budget runs out while a worker is still running. That worker may
+// budget runs out while a worker is still running. The archive
-// be in the middle of an archive write, so the archive writers are
+// writers are left open, as a kill would leave them: closing them
-// left open, as a kill would leave them, rather than closed
+// would wait for any write in progress, and that worker would then
-// underneath it.
+// open new writers that nothing closes.
 func TestEngine_StopHookTimeoutLeavesArchivesOpen(t *testing.T) {
 	t.Parallel()