feat: AI Writer inline — génère du contenu au curseur

- Mode 'write' ajouté à paragraph-refactor.service.ts
- Endpoint /api/ai/reformulate étendu (option 'write' + writePrompt)
- UI : champ de prompt inline apparaît au curseur après slash menu
  - Tape / → 'Écrire avec l'IA' → décrit ce que tu veux → Entrée
  - L'IA génère et insère le contenu à la position du curseur
- Pas de migration DB, réutilise l'infra existante
- i18n FR/EN

memento-note/app/api/ai/reformulate/route.ts

@@ -23,39 +23,37 @@ export async function POST(request: NextRequest) {
       return NextResponse.json({ error: 'Feature disabled' }, { status: 403 })
     }
 
-    const { text, option, format, language } = await request.json()
-
-    // Validation
-    if (!text || typeof text !== 'string') {
-      return NextResponse.json({ error: 'Text is required' }, { status: 400 })
-    }
+    const { text, option, format, language, writePrompt } = await request.json()
 
     // Map option to refactor mode
-    const modeMap: Record<string, 'clarify' | 'shorten' | 'improveStyle' | 'fix_grammar' | 'translate' | 'explain'> = {
+    const modeMap: Record<string, 'clarify' | 'shorten' | 'improveStyle' | 'fix_grammar' | 'translate' | 'explain' | 'write'> = {
       'clarify': 'clarify',
       'shorten': 'shorten',
       'improve': 'improveStyle',
       'fix_grammar': 'fix_grammar',
       'translate': 'translate',
-      'explain': 'explain'
+      'explain': 'explain',
+      'write': 'write'
     }
 
     const mode = modeMap[option]
     if (!mode) {
       return NextResponse.json(
-        { error: 'Invalid option. Use: clarify, shorten, improve, fix_grammar, translate, or explain' },
+        { error: 'Invalid option. Use: clarify, shorten, improve, fix_grammar, translate, explain, or write' },
         { status: 400 }
       )
     }
 
-    // Validate word count
-    const validation = paragraphRefactorService.validateWordCount(text)
-    if (!validation.valid) {
-      return NextResponse.json({
-        error: validation.error,
-        errorKey: validation.errorKey,
-        params: validation.params,
-      }, { status: 400 })
+    // Validate word count (skip for 'write' mode — no selection needed)
+    if (mode !== 'write') {
+      const validation = paragraphRefactorService.validateWordCount(text)
+      if (!validation.valid) {
+        return NextResponse.json({
+          error: validation.error,
+          errorKey: validation.errorKey,
+          params: validation.params,
+        }, { status: 400 })
+      }
     }
 
     // Check quota
@@ -75,7 +73,7 @@ export async function POST(request: NextRequest) {
     }
 
     // Use the ParagraphRefactorService
-    const result = await paragraphRefactorService.refactor(text, mode, format === 'html' ? 'html' : 'markdown', language)
+    const result = await paragraphRefactorService.refactor(text, mode, format === 'html' ? 'html' : 'markdown', language, writePrompt)
 
     incrementUsageAsync(session.user.id, 'reformulate')