feat(ui): unify child surfaces and show web task creation in a modal (#1633)

ui/flutter/lib/core/window/app_window_bootstrap.dart

@@ -4,6 +4,7 @@ import 'package:flutter/widgets.dart';
 import 'package:window_manager/window_manager.dart';
 
 import '../../l10n/l10n.dart';
+import '../../shared/theme/app_design_tokens.dart';
 import 'app_window_chrome.dart';
 import 'app_window_payload.dart';
 
@@ -46,7 +47,7 @@ class AppWindowBootstrap {
 
     final options = switch (type) {
       AppWindowType.createTask => WindowOptions(
-        size: Size(820, 620),
+        size: AppDesignTokens.childWindowSize,
         center: true,
         skipTaskbar: false,
         backgroundColor: Colors.transparent,

ui/flutter/lib/core/window/app_window_launcher.dart

@@ -2,22 +2,24 @@ import 'dart:io';
 
 import 'package:desktop_multi_window/desktop_multi_window.dart';
 import 'package:flutter/foundation.dart';
+import 'package:window_manager/window_manager.dart';
 
-import '../../api/model/create_task.dart';
 import '../../util/log_util.dart';
 import '../capabilities/app_capabilities.dart';
 import 'app_window_payload.dart';
 import 'window_capability_transport.dart';
 
 class AppWindowLauncher {
-  static Future<bool> openCreateTaskWindow({CreateTask? createTask}) async {
+  static Future<bool> open(AppWindowPayload payload) async {
+    if (payload.type == AppWindowType.main) {
+      throw ArgumentError.value(payload.type, 'payload.type', 'Expected a child window');
+    }
     if (kIsWeb || !(Platform.isWindows || Platform.isMacOS || Platform.isLinux)) {
       return false;
     }
 
     try {
       await AppWindowCapabilityHost.instance.start(LocalAppCapabilities.instance.registry);
-      final payload = AppWindowPayload.createTask(createTask: createTask?.toJson());
       // Every request deliberately creates a new child window. Create-task
       // windows are independent and are never reused.
       await WindowController.create(WindowConfiguration(arguments: payload.toRaw(), hiddenAtLaunch: true));
@@ -27,10 +29,16 @@ class AppWindowLauncher {
       return true;
     } catch (error, stackTrace) {
       try {
-        logger.w('create task window failed', error, stackTrace);
+        logger.w('child window failed', error, stackTrace);
       } catch (_) {
-        debugPrint('create task window failed: $error');
+        debugPrint('child window failed: $error');
       }
+      // A tray/deep-link request can arrive while the main window is hidden.
+      // Bring the in-app fallback into view if the child engine cannot start.
+      try {
+        await windowManager.show();
+        await windowManager.focus();
+      } catch (_) {}
       return false;
     }
   }