fix(tsconnect): address bridge review findings

Co-Authored-By: gpt-5.6-sol <noreply@openai.com>

cmd/tsconnect/wasm/drive.go

@@ -138,7 +138,7 @@ func (fs *jsFileSystemForRemote) ServeHTTPWithPerms(
 	readBodyChunk := js.FuncOf(func(_ js.Value, _ []js.Value) any {
 		if !response.isLive() {
 			return makePromise(func() (any, error) {
-				return nil, errors.New("drive request is closed")
+				return js.Null(), nil
 			})
 		}
 		return makePromise(func() (any, error) {
@@ -176,26 +176,35 @@ func (fs *jsFileSystemForRemote) ServeHTTPWithPerms(
 		}
 		return nil
 	})
-	rejected := js.FuncOf(func(_ js.Value, args []js.Value) any {
+	var fulfilled, rejected js.Func
+	var handlerSettled sync.Once
+	settleHandler := func(err error) {
+		handlerSettled.Do(func() {
+			select {
+			case response.doneCh <- err:
+			default:
+			}
+			readBodyChunk.Release()
+			writeHead.Release()
+			write.Release()
+			end.Release()
+			fulfilled.Release()
+			rejected.Release()
+		})
+	}
+	fulfilled = js.FuncOf(func(_ js.Value, _ []js.Value) any {
+		settleHandler(nil)
+		return nil
+	})
+	rejected = js.FuncOf(func(_ js.Value, args []js.Value) any {
 		err := errors.New("JavaScript drive handler rejected")
 		if len(args) > 0 && args[0].Type() == js.TypeString {
 			err = fmt.Errorf("JavaScript drive handler rejected: %s", args[0].String())
 		}
-		select {
-		case response.doneCh <- err:
-		default:
-		}
+		settleHandler(err)
 		return nil
 	})
 
-	defer func() {
-		readBodyChunk.Release()
-		writeHead.Release()
-		write.Release()
-		end.Release()
-		rejected.Release()
-	}()
-
 	jsReq := map[string]any{
 		"method":        r.Method,
 		"path":          r.URL.Path,
@@ -214,14 +223,13 @@ func (fs *jsFileSystemForRemote) ServeHTTPWithPerms(
 		if hasThen, err := hasJSFunctionProperty(result, "then"); err != nil {
 			handlerErr = err
 		} else if hasThen {
-			_, handlerErr = callJSMethod(result, "then", js.Undefined(), rejected)
+			_, handlerErr = callJSMethod(result, "then", fulfilled, rejected)
+		} else {
+			settleHandler(nil)
 		}
 	}
 	if handlerErr != nil {
-		select {
-		case response.doneCh <- handlerErr:
-		default:
-		}
+		settleHandler(handlerErr)
 	}
 
 	var resultErr error