feat: add experimental session memory source

src/sessions/transcript-events.ts

@@ -0,0 +1,23 @@
+type SessionTranscriptUpdate = {
+  sessionFile: string;
+};
+
+type SessionTranscriptListener = (update: SessionTranscriptUpdate) => void;
+
+const SESSION_TRANSCRIPT_LISTENERS = new Set<SessionTranscriptListener>();
+
+export function onSessionTranscriptUpdate(listener: SessionTranscriptListener): () => void {
+  SESSION_TRANSCRIPT_LISTENERS.add(listener);
+  return () => {
+    SESSION_TRANSCRIPT_LISTENERS.delete(listener);
+  };
+}
+
+export function emitSessionTranscriptUpdate(sessionFile: string): void {
+  const trimmed = sessionFile.trim();
+  if (!trimmed) return;
+  const update = { sessionFile: trimmed };
+  for (const listener of SESSION_TRANSCRIPT_LISTENERS) {
+    listener(update);
+  }
+}