feat(client): adopt the locale seat in theme, sidebar, question, and model

Each package ships its zh/en dictionaries as satisfies-typed pairs (zh is
the key-set source of truth; en is checked complete against it), merges its
namespace into LocaleNamespaceMap, and declares locale: NS at register —
components read the framework-injected typed t seat instead of a
hand-carried inject member. Overlapping verbatim words (retry, submit,
submitting) drop out of package dictionaries in favor of the shared common
vocabulary; the question composer stores validation feedback as dictionary
keys so shown feedback follows a locale switch.

packages/client/ui-question/src/client/QuestionComposer.tsx

@@ -65,7 +65,10 @@ function QuestionFlow({ pending, t }: { pending: PendingQuestion } & Pick<Questi
     selected: [], custom: '', customOpen: (question.options?.length ?? 0) === 0, skipped: false,
   })))
   const [busy, setBusy] = useState<'answer' | 'cancel' | null>(null)
-  const [error, setError] = useState<string | null>(null)
+  // Validation feedback is stored as a dictionary KEY and translated at
+  // render, so already-shown feedback follows a locale switch; runtime
+  // failure messages (finished strings from the wire) pass through verbatim.
+  const [error, setError] = useState<{ key: 'error.incomplete' | 'error.unanswered' } | { text: string } | null>(null)
   // index stays in bounds (every setIndex site clamps) and drafts mirrors questions 1:1.
   // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
   const question = questions[index]!
@@ -78,7 +81,7 @@ function QuestionFlow({ pending, t }: { pending: PendingQuestion } & Pick<Questi
     setError(null)
     void pending.cancel().catch((cause: unknown) => {
       setBusy(null)
-      setError(cause instanceof Error ? cause.message : String(cause))
+      setError({ text: cause instanceof Error ? cause.message : String(cause) })
     })
   }
 
@@ -114,7 +117,7 @@ function QuestionFlow({ pending, t }: { pending: PendingQuestion } & Pick<Questi
     const missing = values.findIndex(item => !completed(item))
     if (missing >= 0) {
       setIndex(missing)
-      setError(t('error.incomplete'))
+      setError({ key: 'error.incomplete' })
       return
     }
     const answer: QuestionAnswer = {
@@ -133,13 +136,13 @@ function QuestionFlow({ pending, t }: { pending: PendingQuestion } & Pick<Questi
     setError(null)
     void pending.answer(answer).catch((cause: unknown) => {
       setBusy(null)
-      setError(cause instanceof Error ? cause.message : String(cause))
+      setError({ text: cause instanceof Error ? cause.message : String(cause) })
     })
   }
 
   const continueFlow = (): void => {
     if (!answered(draft)) {
-      setError(t('error.unanswered'))
+      setError({ key: 'error.unanswered' })
       return
     }
     if (index < questions.length - 1) {
@@ -292,7 +295,7 @@ function QuestionFlow({ pending, t }: { pending: PendingQuestion } & Pick<Questi
         </div>
 
         <footer className={css.footer}>
-          <div className={css.feedback} role="status">{error}</div>
+          <div className={css.feedback} role="status">{error === null ? null : 'key' in error ? t(error.key) : error.text}</div>
           <div className={css.footerActions}>
             <Button variant="ghost" size="sm" disabled={busy !== null} onClick={skipQuestion}>
               {t('action.skip')}
@@ -302,8 +305,8 @@ function QuestionFlow({ pending, t }: { pending: PendingQuestion } & Pick<Questi
               disabled={busy !== null || !answered(draft)} onClick={continueFlow}
             >
               {busy === 'answer'
-                ? t('action.submitting')
-                : index === questions.length - 1 ? t('action.submit') : t('action.next')}
+                ? t('submitting')
+                : index === questions.length - 1 ? t('submit') : t('action.next')}
             </Button>
           </div>
         </footer>

packages/client/ui-question/src/client/locales.ts

@@ -12,8 +12,6 @@ export const zh = {
   'option.custom': '其他，请填写自定义答案',
   'custom.placeholder': '输入你的答案',
   'action.skip': '跳过本题',
-  'action.submitting': '正在提交…',
-  'action.submit': '提交',
   'action.next': '下一题',
 } satisfies Record<string, string>
 
@@ -21,7 +19,7 @@ export const zh = {
 export type QuestionKey = keyof typeof zh
 
 /** English dictionary, checked complete against the zh key set. */
-export const en: Record<QuestionKey, string> = {
+export const en = {
   'error.incomplete': 'Please complete this question first.',
   'error.unanswered': 'Please select an option or enter a custom answer.',
   'title.multi': 'Multi-select',
@@ -32,7 +30,5 @@ export const en: Record<QuestionKey, string> = {
   'option.custom': 'Other — enter a custom answer',
   'custom.placeholder': 'Type your answer',
   'action.skip': 'Skip this question',
-  'action.submitting': 'Submitting…',
-  'action.submit': 'Submit',
   'action.next': 'Next',
-}
+} satisfies Record<QuestionKey, string>