[05-Designer] #260 chat UX polish (QA 인수 4건)

QA round 2 인수 노트의 UX 항목 정돈. blocker 아니었음 — Designer 단계
의무 폴리시.

1) ToolCallChatMessage 라벨 한국어화
   - chat_screen.dart: _kToolKoreanLabels 맵 추가. 6 tool 모두 한국어
     라벨 (예: add_habit → '습관 추가'). 미매핑 tool 은 raw name fallback.

2) ConfirmDialog 좁은 화면 reflow
   - confirm_gate.dart: AlertDialog content 를 SingleChildScrollView 로
     감쌈. summary box width=double.infinity (좌측 정렬 안정).

3) Streaming cursor 다크모드 contrast
   - chat_screen.dart: ▍ 문자를 Text.rich 로 분리해 colorScheme.primary
     적용. 다크 모드에서도 onSurface 본문 대비 cursor 가 식별됨.

4) AppBar tooltip 명료성
   - chat_screen.dart: '새 대화' → '새 대화 (이전 기록 비우기)'.
     history reset 의미 명시.

회귀
- 154 passed (1 skip), 회귀 0
- flutter analyze: clean

Refs #260

app/lib/ai/tools/confirm_gate.dart

@@ -27,21 +27,26 @@ class ConfirmGate {
         final theme = Theme.of(ctx);
         return AlertDialog(
           title: const Text('이 작업을 수행할까요?'),
-          content: Column(
-            mainAxisSize: MainAxisSize.min,
-            crossAxisAlignment: CrossAxisAlignment.start,
-            children: [
-              Text(tool.description, style: theme.textTheme.bodyMedium),
-              const SizedBox(height: 12),
-              Container(
-                padding: const EdgeInsets.all(12),
-                decoration: BoxDecoration(
-                  color: theme.colorScheme.surfaceContainerHighest,
-                  borderRadius: BorderRadius.circular(8),
+          // SingleChildScrollView 로 감싸 좁은 모바일 화면에서 description 이
+          // 길거나 summary 가 multi-line 일 때 잘리지 않고 스크롤되게 한다.
+          content: SingleChildScrollView(
+            child: Column(
+              mainAxisSize: MainAxisSize.min,
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: [
+                Text(tool.description, style: theme.textTheme.bodyMedium),
+                const SizedBox(height: 12),
+                Container(
+                  width: double.infinity,
+                  padding: const EdgeInsets.all(12),
+                  decoration: BoxDecoration(
+                    color: theme.colorScheme.surfaceContainerHighest,
+                    borderRadius: BorderRadius.circular(8),
+                  ),
+                  child: Text(summary),
                 ),
-                child: Text(summary),
-              ),
-            ],
+              ],
+            ),
           ),
           actions: [
             TextButton(

app/lib/ui/screens/chat_screen.dart

@@ -55,7 +55,7 @@ class _ChatScreenState extends ConsumerState<ChatScreen> {
         actions: [
           IconButton(
             icon: const Icon(Icons.refresh),
-            tooltip: '새 대화',
+            tooltip: '새 대화 (이전 기록 비우기)',
             onPressed: () {
               ref.read(chatSessionControllerProvider.notifier).clear();
             },
@@ -150,6 +150,19 @@ class _ChatScreenState extends ConsumerState<ChatScreen> {
   }
 }
 
+/// Human-friendly Korean labels for the 6 tools registered in
+/// `ToolRegistry.defaults()`. Falls back to the raw tool name for any
+/// future tool that hasn't been mapped yet — better to show the raw id
+/// than to silently drop the message.
+const Map<String, String> _kToolKoreanLabels = {
+  'search_catalog': '카탈로그 검색',
+  'query_protocol': '프로토콜 상세',
+  'list_active_habits': '활성 습관 조회',
+  'get_streak': '스트릭 조회',
+  'add_habit': '습관 추가',
+  'log_tracker_entry': '체크 기록',
+};
+
 class _MessageBubble extends StatelessWidget {
   final ChatMessage message;
   final bool streaming;
@@ -168,14 +181,29 @@ class _MessageBubble extends StatelessWidget {
           text: m.text,
         );
       case ModelChatMessage m:
+        // Streaming cursor uses primary so it stays discoverable in both
+        // light and dark themes (default onSurface low-contrasted with the
+        // surfaceContainerHighest bubble in dark mode).
         return _bubble(
           context,
           align: Alignment.centerLeft,
           color: theme.colorScheme.surfaceContainerHighest,
           textColor: theme.colorScheme.onSurface,
-          text: m.text + (streaming ? '▍' : ''),
+          richText: streaming
+              ? TextSpan(
+                  children: [
+                    TextSpan(text: m.text),
+                    TextSpan(
+                      text: '▍',
+                      style: TextStyle(color: theme.colorScheme.primary),
+                    ),
+                  ],
+                )
+              : null,
+          text: m.text,
         );
       case ToolCallChatMessage m:
+        final label = _kToolKoreanLabels[m.name] ?? m.name;
         return Align(
           alignment: Alignment.center,
           child: Container(
@@ -187,8 +215,9 @@ class _MessageBubble extends StatelessWidget {
               border: Border.all(color: theme.colorScheme.outlineVariant),
             ),
             child: Text(
-              '🛠 ${m.name} → ${_toolResultLabel(m.result)}',
+              '🛠 $label → ${_toolResultLabel(m.result)}',
               style: theme.textTheme.bodySmall,
+              textAlign: TextAlign.center,
             ),
           ),
         );
@@ -212,6 +241,7 @@ class _MessageBubble extends StatelessWidget {
     required Color color,
     required Color textColor,
     required String text,
+    TextSpan? richText,
   }) {
     return Align(
       alignment: align,
@@ -225,7 +255,9 @@ class _MessageBubble extends StatelessWidget {
           color: color,
           borderRadius: BorderRadius.circular(12),
         ),
-        child: Text(text, style: TextStyle(color: textColor)),
+        child: richText != null
+            ? Text.rich(richText, style: TextStyle(color: textColor))
+            : Text(text, style: TextStyle(color: textColor)),
       ),
     );
   }