test(web): the 499 test cancels the client mid-Accept, as a real hang-up does

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/web/uploads_disconnect_handler_test.go

@@ -81,6 +81,15 @@ func TestUploadPost_AClientThatHangsUpAnywhereInTheBodyIsLoggedAtInfoAndNeverAsA
 	}
 }
 
+// goneMidAccept is an Uploader during whose Accept the client disappears: the request's
+// context is cancelled, then Accept fails the way a read from a dead connection does.
+type goneMidAccept struct{ cancel context.CancelFunc }
+
+func (g goneMidAccept) Accept(context.Context, string, string, io.Reader) (string, error) {
+	g.cancel()
+	return "", fmt.Errorf("receive: %w", io.ErrClosedPipe)
+}
+
 func TestUploadPost_AnAbandonedRequestGetsA499NotAnImplicitEmpty200(t *testing.T) {
 	// If the context is cancelled but the connection can still be written to (a client that
 	// half-closed after sending), a missing status becomes 200 with an empty body: a false
@@ -88,12 +97,11 @@ func TestUploadPost_AnAbandonedRequestGetsA499NotAnImplicitEmpty200(t *testing.T
 	app, _ := newUploadApp(t, audioOK, 200<<20)
 	buf := &lockedBuf{}
 	app.Log = slog.New(slog.NewTextHandler(buf, nil))
-	app.Uploads = failingUploader{err: fmt.Errorf("receive: %w", io.ErrClosedPipe)}
 	ctx, cancel := context.WithCancel(context.Background())
-	cancel()
-	req := uploadReq(t, "t", "a.m4a", []byte("x")).WithContext(ctx)
+	defer cancel()
+	app.Uploads = goneMidAccept{cancel: cancel}
 
-	rec := do(t, app, req)
+	rec := do(t, app, uploadReq(t, "t", "a.m4a", []byte("x")).WithContext(ctx))
 
 	assert.Equal(t, 499, rec.Code, "never an implicit 200 for an upload that was not accepted")
 	assert.Contains(t, buf.String(), "upload abandoned")