Quit guard during transfers + background completion notifications

- before-quit is blocked while jobs are queued/scanning/running; a native
  message box asks 'N transfers are still running - quit anyway?' (Cancel
  default) and only an explicit Quit Anyway proceeds via Utils.quit()
- when the window is unfocused, finished transfers raise a native
  notification (silent for completions, sound + error message for failures)
- engine.hasActiveJobs()/activeJobCount() (truth table verified headless)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/bun/index.ts

@@ -1,4 +1,4 @@
-import { ApplicationMenu, BrowserWindow, Updater } from "electrobun/bun";
+import Electrobun, { ApplicationMenu, BrowserWindow, Updater, Utils } from "electrobun/bun";
 import { BRANDING } from "../shared/branding";
 import { effectiveConcurrency } from "../shared/types";
 import { PanelContextMenu } from "./context-menu";
@@ -69,7 +69,57 @@ const win = new BrowserWindow({
 new AppTray(win);
 contextMenu.onAction = (action) => rpc.send.menuAction({ action });
 
-engine.onUpdate = (snapshot) => rpc.send.transferUpdate(snapshot);
+// notify on finished transfers while the window is in the background
+let windowFocused = true;
+win.on("focus", () => (windowFocused = true));
+win.on("blur", () => (windowFocused = false));
+const notifiedStates = new Map<string, string>();
+
+engine.onUpdate = (snapshot) => {
+	rpc.send.transferUpdate(snapshot);
+
+	const previous = notifiedStates.get(snapshot.id);
+	if (previous !== snapshot.state) {
+		notifiedStates.set(snapshot.id, snapshot.state);
+		if (!windowFocused && (snapshot.state === "completed" || snapshot.state === "failed")) {
+			Utils.showNotification({
+				title: snapshot.state === "completed" ? "Transfer complete" : "Transfer failed",
+				body:
+					snapshot.state === "completed"
+						? snapshot.name
+						: `${snapshot.name}: ${snapshot.error ?? "unknown error"}`,
+				silent: snapshot.state === "completed",
+			});
+		}
+		if (snapshot.state === "completed" || snapshot.state === "failed" || snapshot.state === "cancelled") {
+			// keep the map from growing over long sessions
+			setTimeout(() => notifiedStates.delete(snapshot.id), 60_000);
+		}
+	}
+};
+
+// don't quit out from under running transfers
+let quitConfirmed = false;
+Electrobun.events.on("before-quit", (event) => {
+	if (quitConfirmed || !engine.hasActiveJobs()) return;
+	(event as { response: { allow: boolean } }).response = { allow: false };
+	void (async () => {
+		const count = engine.activeJobCount();
+		const { response } = await Utils.showMessageBox({
+			type: "warning",
+			title: BRANDING.appName,
+			message: `${count} transfer${count === 1 ? " is" : "s are"} still running.`,
+			detail: "Quitting now will abort them.",
+			buttons: ["Quit Anyway", "Cancel"],
+			defaultId: 1,
+			cancelId: 1,
+		});
+		if (response === 0) {
+			quitConfirmed = true;
+			Utils.quit();
+		}
+	})();
+});
 events.sessionClosed = (info) => rpc.send.sessionClosed(info);
 events.connectionsChanged = () => void applyApplicationMenu(store);
 void settings.load().then((s) => engine.setConcurrency(effectiveConcurrency(s)));

src/bun/transfers/engine.ts

@@ -146,6 +146,22 @@ export class TransferEngine {
 		if (job && TERMINAL.includes(job.snapshot.state)) this.jobs.delete(jobId);
 	}
 
+	/** True while any job is queued, scanning or running (quit guard). */
+	hasActiveJobs(): boolean {
+		for (const job of this.jobs.values()) {
+			if (!TERMINAL.includes(job.snapshot.state)) return true;
+		}
+		return false;
+	}
+
+	activeJobCount(): number {
+		let count = 0;
+		for (const job of this.jobs.values()) {
+			if (!TERMINAL.includes(job.snapshot.state)) count++;
+		}
+		return count;
+	}
+
 	/** Fail every non-terminal job that touches a dead session. */
 	failSession(sessionId: string, reason: string): void {
 		for (const job of this.jobs.values()) {