feat(nexus): OS notification + terminal bell when sub-agent finishes

extensions/nexus.ts

@@ -514,6 +514,18 @@ export default function nexus(pi: ExtensionAPI) {
 		});
 	}
 
+	function notifyOS(title: string, message: string) {
+		// macOS notification via osascript
+		try {
+			cpSpawn("osascript", [
+				"-e",
+				`display notification "${message.replace(/"/g, '\\"')}" with title "${title.replace(/"/g, '\\"')}" sound name "Glass"`,
+			], { stdio: "ignore", detached: true }).unref();
+		} catch {}
+		// Also ring the terminal bell as fallback
+		process.stdout.write("\x07");
+	}
+
 	function spawnAndDeliver(a: SubAgent, prompt: string, ctx: ExtensionContext, isCont: boolean) {
 		spawnProcess(a, prompt, ctx, isCont).then(({ output, exitCode }) => {
 			const status = exitCode === 0 ? "✓" : "✗";
@@ -523,6 +535,12 @@ export default function nexus(pi: ExtensionAPI) {
 
 			ctx.ui.notify(`#${a.id} [${a.role}] ${status} ${elapsed}s`, exitCode === 0 ? "info" : "error");
 
+			// 🔔 OS notification so user is alerted even when away from terminal
+			notifyOS(
+				`Nexus #${a.id} [${a.role}] ${status}`,
+				`${elapsed}s · ${a.toolCount} tools · ${a.task.slice(0, 60)}`,
+			);
+
 			pi.sendMessage({
 				customType: "nexus-result",
 				content: `**Sub-agent #${a.id}** [${a.role}]${turn} — ${status} ${elapsed}s | ${a.toolCount} tools | $${a.cost.toFixed(4)}\n\n${truncated}`,