style: use plain ASCII dashes in comment section divider

Author: dilanmelvin

src/backend/drivers/ai-chat/providers/mistral/MistralAiProvider.test.ts

@@ -655,7 +655,7 @@ describe('MistralAIProvider.complete streaming', () => {
     });
 });
 
-// ── Mistral image_url coercion ──────────────────────────────────────
+// -- Mistral image_url coercion --
 
 describe('MistralAIProvider image_url coercion', () => {
     const baseCompletion = {