fix(desktop): say a sub-second reasoning block was brief

The elapsed timer counts whole seconds, so reasoning that finished
inside one rendered as "Thought for 0s" — accurate and useless, and on a
turn with several short blocks it repeats down the transcript. Drop the
number below a second and say it was brief instead.

apps/desktop/src/components/assistant-ui/thread/message-parts.tsx

@@ -89,6 +89,15 @@ const ThinkingDisclosure: FC<{
     }
   }, [elapsed, pending, watching])
 
+  // The timer counts whole seconds, so a block that finished inside one reports
+  // "0s" — accurate and useless. Say it was quick and leave the number out.
+  const thoughtLabel =
+    pending || thoughtFor === null
+      ? t.assistant.thread.thinking
+      : thoughtFor < 1
+        ? t.assistant.thread.thoughtBriefly
+        : t.assistant.thread.thoughtFor(formatElapsed(thoughtFor))
+
   // While the preview is live, pin the scroll container to the bottom on
   // every content growth so the latest tokens are always visible.
   useEffect(() => {
@@ -143,9 +152,7 @@ const ThinkingDisclosure: FC<{
               pending && 'shimmer text-foreground/55'
             )}
           >
-            {pending || thoughtFor === null
-              ? t.assistant.thread.thinking
-              : t.assistant.thread.thoughtFor(formatElapsed(thoughtFor))}
+            {thoughtLabel}
           </span>
           {pending && (
             <ActivityTimerText

apps/desktop/src/i18n/ar.ts

@@ -2273,6 +2273,7 @@ export const ar = defineLocale({
       resumeWhenBackgroundDone: count =>
         count === 1 ? 'سيُستأنف عند انتهاء المهمة الخلفية' : `سيُستأنف عند انتهاء ${count} مهام خلفية`,
       thinking: 'يفكر...',
+      thoughtBriefly: 'فكّر قليلاً',
       thoughtFor: duration => `فكّر لمدة ${duration}`,
       today: time => `اليوم ${time}`,
       yesterday: time => `أمس ${time}`,

apps/desktop/src/i18n/en.ts

@@ -2668,6 +2668,7 @@ export const en: Translations = {
           ? 'Will resume when the background task finishes'
           : `Will resume when ${count} background tasks finish`,
       thinking: 'Thinking',
+      thoughtBriefly: 'Thought briefly',
       thoughtFor: duration => `Thought for ${duration}`,
       today: time => `Today, ${time}`,
       yesterday: time => `Yesterday, ${time}`,

apps/desktop/src/i18n/ja.ts

@@ -2517,6 +2517,7 @@ export const ja = defineLocale({
           ? 'バックグラウンドタスクの完了後に再開します'
           : `${count} 件のバックグラウンドタスクの完了後に再開します`,
       thinking: '考え中',
+      thoughtBriefly: '少し思考',
       thoughtFor: duration => `${duration} 思考`,
       today: time => `今日 ${time}`,
       yesterday: time => `昨日 ${time}`,

apps/desktop/src/i18n/types.ts

@@ -2267,6 +2267,7 @@ export interface Translations {
       loadingResponse: string
       resumeWhenBackgroundDone: (count: number) => string
       thinking: string
+      thoughtBriefly: string
       thoughtFor: (duration: string) => string
       today: (time: string) => string
       yesterday: (time: string) => string

apps/desktop/src/i18n/zh-hant.ts

@@ -2438,6 +2438,7 @@ export const zhHant = defineLocale({
       resumeWhenBackgroundDone: count =>
         count === 1 ? '背景工作完成後將自動繼續' : `${count} 個背景工作完成後將自動繼續`,
       thinking: '思考中',
+      thoughtBriefly: '思考了片刻',
       thoughtFor: duration => `思考了 ${duration}`,
       today: time => `今天，${time}`,
       yesterday: time => `昨天，${time}`,

apps/desktop/src/i18n/zh.ts

@@ -2839,6 +2839,7 @@ export const zh: Translations = {
       resumeWhenBackgroundDone: count =>
         count === 1 ? '后台任务完成后将自动继续' : `${count} 个后台任务完成后将自动继续`,
       thinking: '思考中',
+      thoughtBriefly: '思考了片刻',
       thoughtFor: duration => `思考了 ${duration}`,
       today: time => `今天，${time}`,
       yesterday: time => `昨天，${time}`,