feat: add translated PDF format selection (layout/reflow)

- Add generate_translated_layout_pdf() method for layout-preserving translated PDFs
- Add generate_translated_pdf() method for reflow translated PDFs
- Update translate router to accept format parameter (layout/reflow)
- Update frontend with dropdown to select translated PDF format
- Fix reflow PDF table cell extraction from content dict
- Add embedded images handling in reflow PDF tables
- Archive improve-translated-text-fitting openspec proposal

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/services/apiV2.ts

@@ -494,16 +494,20 @@ class ApiClientV2 {
 
   /**
    * Download task result as PDF
+   * @param taskId - The task ID
+   * @param format - PDF format: 'layout' (default) or 'reflow'
    */
-  async downloadPDF(taskId: string): Promise<void> {
+  async downloadPDF(taskId: string, format: 'layout' | 'reflow' = 'layout'): Promise<void> {
     const response = await this.client.get(`/tasks/${taskId}/download/pdf`, {
+      params: format === 'reflow' ? { format: 'reflow' } : undefined,
       responseType: 'blob',
     })
 
     const blob = new Blob([response.data], { type: 'application/pdf' })
     const link = document.createElement('a')
     link.href = window.URL.createObjectURL(blob)
-    link.download = `${taskId}_result.pdf`
+    const formatSuffix = format === 'reflow' ? '_reflow' : '_layout'
+    link.download = `${taskId}${formatSuffix}.pdf`
     link.click()
     window.URL.revokeObjectURL(link.href)
   }
@@ -688,18 +692,26 @@ class ApiClientV2 {
   }
 
   /**
-   * Download translated PDF with layout preservation
+   * Download translated PDF
+   * @param taskId - The task ID
+   * @param lang - Target language code
+   * @param format - PDF format: 'layout' or 'reflow' (default: 'reflow')
    */
-  async downloadTranslatedPdf(taskId: string, lang: string): Promise<void> {
+  async downloadTranslatedPdf(
+    taskId: string,
+    lang: string,
+    format: 'layout' | 'reflow' = 'reflow'
+  ): Promise<void> {
     const response = await this.client.post(`/translate/${taskId}/pdf`, null, {
-      params: { lang },
+      params: { lang, format },
       responseType: 'blob',
     })
 
+    const formatSuffix = format === 'layout' ? '_layout' : '_reflow'
     const blob = new Blob([response.data], { type: 'application/pdf' })
     const link = document.createElement('a')
     link.href = window.URL.createObjectURL(blob)
-    link.download = `${taskId}_translated_${lang}.pdf`
+    link.download = `${taskId}_translated_${lang}${formatSuffix}.pdf`
     link.click()
     window.URL.revokeObjectURL(link.href)
   }