Run server-engine file transcriptions through faster-whisper's batched pipeline with VAD

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/server/transcribe.ts

@@ -47,8 +47,15 @@ export interface SidecarTranscribeRequest {
   audioPath: string;
   language?: string;
   task?: WhisperTask;
+  /**
+   * "file" (default): whole uploads — batched inference over VAD speech
+   * chunks. "live": short server-live passes — sequential, no VAD (D-WS5a).
+   */
+  mode?: SidecarMode;
 }
 
+export type SidecarMode = "file" | "live";
+
 export interface SidecarStatus {
   available: boolean;
   reason?: string;
@@ -265,6 +272,7 @@ export function createSidecar(command?: readonly string[]): Sidecar {
             audio_path: request.audioPath,
             language: request.language ?? null,
             task: request.task ?? "transcribe",
+            mode: request.mode ?? "file",
           });
         } catch (error) {
           pending.delete(id);