test(flutter/theme): cover .dark()/.light() factories + back-compat alias

Four cases: dark factory pulls from FabledSwordDarkTokens, light from
FabledSwordLightTokens, flat tokens (accent / moss / etc.) are shared
between both, and the fromTokens() back-compat alias returns the dark
theme.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

flutter_client/test/theme/theme_extension_test.dart

@@ -1,26 +1,39 @@
-import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 
-import 'package:minstrel/theme/theme_data.dart';
 import 'package:minstrel/theme/theme_extension.dart';
 import 'package:minstrel/theme/tokens.dart';
 
 void main() {
-  testWidgets('Theme exposes FabledSwordTheme with expected accent', (tester) async {
-    late FabledSwordTheme captured;
-    await tester.pumpWidget(
-      MaterialApp(
-        theme: buildThemeData(),
-        home: Builder(
-          builder: (ctx) {
-            captured = Theme.of(ctx).extension<FabledSwordTheme>()!;
-            return const SizedBox.shrink();
-          },
-        ),
-      ),
-    );
-    expect(captured.accent, FabledSwordTokens.accent);
-    expect(captured.parchment, FabledSwordTokens.parchment);
-    expect(captured.body.fontFamily, FabledSwordTokens.fontBody);
+  test('FabledSwordTheme.dark uses dark surface tokens', () {
+    final fs = FabledSwordTheme.dark();
+    expect(fs.obsidian, FabledSwordDarkTokens.obsidian);
+    expect(fs.iron, FabledSwordDarkTokens.iron);
+    expect(fs.parchment, FabledSwordDarkTokens.parchment);
+  });
+
+  test('FabledSwordTheme.light uses light surface tokens', () {
+    final fs = FabledSwordTheme.light();
+    expect(fs.obsidian, FabledSwordLightTokens.obsidian);
+    expect(fs.iron, FabledSwordLightTokens.iron);
+    expect(fs.parchment, FabledSwordLightTokens.parchment);
+  });
+
+  test('flat tokens (accent, moss, etc.) are shared between factories', () {
+    final dark = FabledSwordTheme.dark();
+    final light = FabledSwordTheme.light();
+    expect(dark.accent, light.accent);
+    expect(dark.moss, light.moss);
+    expect(dark.bronze, light.bronze);
+    expect(dark.oxblood, light.oxblood);
+    expect(dark.warning, light.warning);
+    expect(dark.error, light.error);
+    expect(dark.info, light.info);
+  });
+
+  test('fromTokens() back-compat alias returns the dark theme', () {
+    final alias = FabledSwordTheme.fromTokens();
+    final dark = FabledSwordTheme.dark();
+    expect(alias.obsidian, dark.obsidian);
+    expect(alias.parchment, dark.parchment);
   });
 }