Start on live transcription and python sidecar (faster-whisper)

src/worker/protocol.ts

@@ -61,6 +61,12 @@ export interface TranscribeMessage {
   language?: string;
   /** Only meaningful for multilingual models. Defaults to "transcribe". */
   task?: WhisperTask;
+  /**
+   * Optional correlation id, echoed on the partial/result/error messages this
+   * request produces (D-016). The live-transcription loop uses it to match
+   * responses to segment passes; the file flow omits it and is unchanged.
+   */
+  requestId?: string;
 }
 
 export type UiToWorkerMessage = LoadMessage | TranscribeMessage;
@@ -96,6 +102,8 @@ export type LoadProgressMessage =
 export interface PartialMessage {
   type: "partial";
   text: string;
+  /** Echo of the originating transcribe request's id, if it carried one. */
+  requestId?: string;
 }
 
 /** One timestamped segment of the final transcript. */
@@ -109,12 +117,16 @@ export interface ResultMessage {
   type: "result";
   text: string;
   chunks: TranscriptChunk[];
+  /** Echo of the originating transcribe request's id, if it carried one. */
+  requestId?: string;
 }
 
 export interface ErrorMessage {
   type: "error";
   stage: "load" | "transcribe";
   message: string;
+  /** Echo of the failing transcribe request's id, if it carried one. */
+  requestId?: string;
 }
 
 export type WorkerToUiMessage =
@@ -131,6 +143,10 @@ function isRecord(value: unknown): value is Record<string, unknown> {
   return typeof value === "object" && value !== null;
 }
 
+function isOptionalString(value: unknown): value is string | undefined {
+  return value === undefined || typeof value === "string";
+}
+
 const DEVICES: readonly string[] = ["webgpu", "wasm"];
 const DTYPES: readonly string[] = ["fp32", "fp16", "q8", "q4"];
 
@@ -165,10 +181,11 @@ export function isUiToWorkerMessage(value: unknown): value is UiToWorkerMessage
     case "transcribe":
       return (
         value.audio instanceof Float32Array &&
-        (value.language === undefined || typeof value.language === "string") &&
+        isOptionalString(value.language) &&
         (value.task === undefined ||
           value.task === "transcribe" ||
-          value.task === "translate")
+          value.task === "translate") &&
+        isOptionalString(value.requestId)
       );
     default:
       return false;
@@ -197,13 +214,18 @@ export function isWorkerToUiMessage(value: unknown): value is WorkerToUiMessage
           return false;
       }
     case "partial":
-      return typeof value.text === "string";
+      return typeof value.text === "string" && isOptionalString(value.requestId);
     case "result":
-      return typeof value.text === "string" && Array.isArray(value.chunks);
+      return (
+        typeof value.text === "string" &&
+        Array.isArray(value.chunks) &&
+        isOptionalString(value.requestId)
+      );
     case "error":
       return (
         typeof value.message === "string" &&
-        (value.stage === "load" || value.stage === "transcribe")
+        (value.stage === "load" || value.stage === "transcribe") &&
+        isOptionalString(value.requestId)
       );
     default:
       return false;