refactor(sessions): remove transcript truncate

src/sessions/transcriptStore.ts

@@ -147,29 +147,6 @@ export class SessionTranscriptStore {
     return nextTranscript;
   }
 
-  async truncateThread(
-    context: SessionTranscriptContext,
-    keepMessageCount: number,
-  ) {
-    const key = this.filePath(context);
-    return this.serializeWrite(key, async () => {
-      const transcript = await this.readTranscript(context);
-      if (!transcript) {
-        return null;
-      }
-
-      const nextTranscript: SessionTranscriptRecord = {
-        ...transcript,
-        clientSessionId: context.clientSessionId ?? transcript.clientSessionId,
-        sessionId: context.sessionId,
-        turns: projectTurnsForFork(transcript.turns, keepMessageCount),
-        updatedAt: new Date().toISOString(),
-      };
-      await atomicWriteJson(key, nextTranscript);
-      return nextTranscript;
-    });
-  }
-
   async search(
     context: Pick<SessionTranscriptContext, "actorKey" | "projectKey">,
     query: string,