fix(coding-agent): emit session name changes to extensions

packages/coding-agent/test/suite/regressions/3686-session-name-event.test.ts

@@ -37,4 +37,25 @@ describe("regression #3686: session name changes emit an event", () => {
 		expect(harness.sessionManager.getSessionName()).toBe("from extension");
 		expect(harness.eventsOfType("session_info_changed").map((event) => event.name)).toEqual(["from extension"]);
 	});
+
+	it("emits session_info_changed to extensions", async () => {
+		let api: ExtensionAPI | undefined;
+		const events: Array<{ name: string | undefined }> = [];
+		const harness = await createHarness({
+			extensionFactories: [
+				(pi) => {
+					api = pi;
+					pi.on("session_info_changed", (event) => {
+						events.push({ name: event.name });
+					});
+				},
+			],
+		});
+		harnesses.push(harness);
+
+		api?.setSessionName("first");
+		harness.session.setSessionName("second");
+
+		expect(events).toEqual([{ name: "first" }, { name: "second" }]);
+	});
 });