feat(theme): QueryaThemeScope InheritedWidget (#54)

lib/app/app.dart

@@ -1,4 +1,6 @@
 import 'package:querya_desktop/core/theme/app_theme.dart';
+import 'package:querya_desktop/core/theme/querya_theme.dart';
+import 'package:querya_desktop/core/theme/querya_theme_scope.dart';
 import 'package:shadcn_flutter/shadcn_flutter.dart';
 
 import 'app_lifecycle_cleanup.dart';
@@ -19,8 +21,11 @@ class QueryaApp extends StatelessWidget {
       enableThemeAnimation: false,
       // Avoids scroll interception fighting nested Scrollbars in data views.
       enableScrollInterception: false,
-      home: const AppLifecycleCleanup(
-        child: MainScreen(),
+      home: const QueryaThemeScope(
+        data: QueryaTheme.darkDefault,
+        child: AppLifecycleCleanup(
+          child: MainScreen(),
+        ),
       ),
     );
   }

lib/core/theme/querya_theme_scope.dart

@@ -0,0 +1,41 @@
+import 'package:flutter/widgets.dart';
+
+import 'querya_editor_theme.dart';
+import 'querya_theme.dart';
+import 'querya_workbench_theme.dart';
+
+/// Provides [QueryaTheme] (workbench + editor tokens) below [ShadcnApp].
+class QueryaThemeScope extends InheritedWidget {
+  const QueryaThemeScope({
+    super.key,
+    required this.data,
+    required super.child,
+  });
+
+  final QueryaTheme data;
+
+  static QueryaTheme of(BuildContext context) {
+    final scope = context.dependOnInheritedWidgetOfExactType<QueryaThemeScope>();
+    assert(scope != null, 'QueryaThemeScope not found in context');
+    return scope!.data;
+  }
+
+  static QueryaTheme? maybeOf(BuildContext context) {
+    return context
+        .dependOnInheritedWidgetOfExactType<QueryaThemeScope>()
+        ?.data;
+  }
+
+  @override
+  bool updateShouldNotify(QueryaThemeScope oldWidget) =>
+      data != oldWidget.data;
+}
+
+/// Convenient access to [QueryaTheme] tokens from [BuildContext].
+extension QueryaThemeContext on BuildContext {
+  QueryaTheme get queryaTheme => QueryaThemeScope.of(this);
+
+  QueryaWorkbenchTheme get workbench => queryaTheme.workbench;
+
+  QueryaEditorTheme get editorTheme => queryaTheme.editor;
+}

test/core/theme/querya_theme_scope_test.dart

@@ -0,0 +1,81 @@
+import 'package:flutter/material.dart' as material;
+import 'package:flutter_test/flutter_test.dart';
+import 'package:querya_desktop/core/theme/app_theme.dart';
+import 'package:querya_desktop/core/theme/querya_theme.dart';
+import 'package:querya_desktop/core/theme/querya_theme_scope.dart';
+import 'package:shadcn_flutter/shadcn_flutter.dart';
+
+void main() {
+  testWidgets('QueryaThemeScope provides workbench tokens', (tester) async {
+    late Color seenAccent;
+
+    await tester.pumpWidget(
+      ShadcnApp(
+        theme: AppTheme.dark,
+        darkTheme: AppTheme.dark,
+        themeMode: ThemeMode.dark,
+        home: QueryaThemeScope(
+          data: QueryaTheme.darkDefault,
+          child: material.Builder(
+            builder: (context) {
+              seenAccent = context.workbench.accent;
+              return const material.SizedBox();
+            },
+          ),
+        ),
+      ),
+    );
+
+    expect(seenAccent, QueryaTheme.darkDefault.workbench.accent);
+  });
+
+  testWidgets('QueryaThemeScope rebuilds when data changes', (tester) async {
+    var canvas = QueryaTheme.darkDefault.workbench.canvas;
+
+    await tester.pumpWidget(
+      _ScopeHost(
+        data: QueryaTheme.darkDefault,
+        onCanvas: (c) => canvas = c,
+      ),
+    );
+
+    const light = QueryaTheme.lightDefault;
+    await tester.pumpWidget(
+      _ScopeHost(
+        data: light,
+        onCanvas: (c) => canvas = c,
+      ),
+    );
+
+    expect(canvas, light.workbench.canvas);
+    expect(canvas, isNot(QueryaTheme.darkDefault.workbench.canvas));
+  });
+}
+
+class _ScopeHost extends StatelessWidget {
+  const _ScopeHost({
+    required this.data,
+    required this.onCanvas,
+  });
+
+  final QueryaTheme data;
+  final ValueChanged<Color> onCanvas;
+
+  @override
+  Widget build(BuildContext context) {
+    return ShadcnApp(
+      theme: AppTheme.dark,
+      darkTheme: AppTheme.dark,
+      themeMode: ThemeMode.dark,
+      home: QueryaThemeScope(
+        data: data,
+        child: material.Builder(
+          builder: (context) {
+            onCanvas(context.workbench.canvas);
+            return const material.SizedBox();
+          },
+        ),
+      ),
+    );
+  }
+}