fix(browser): canceled settled scroll timers

- Replaced the losing Bun.sleep with an unrefed timeout cleared in a finally block.
- Added regression coverage that verifies prompt wheel acknowledgements leave no timer behind.

Fixes #5905

packages/coding-agent/src/tools/browser/tab-worker.ts

@@ -182,7 +182,14 @@ export async function dispatchScroll(
 	dispatch: () => Promise<void>,
 	ackTimeoutMs = SCROLL_ACK_TIMEOUT_MS,
 ): Promise<void> {
-	await Promise.race([dispatch(), Bun.sleep(ackTimeoutMs)]);
+	const deadline = Promise.withResolvers<void>();
+	const timer = setTimeout(() => deadline.resolve(), ackTimeoutMs);
+	timer.unref();
+	try {
+		await Promise.race([dispatch(), deadline.promise]);
+	} finally {
+		clearTimeout(timer);
+	}
 }
 
 /**

packages/coding-agent/test/tools/browser-tab-timeouts.test.ts

@@ -1,4 +1,4 @@
-import { describe, expect, it } from "bun:test";
+import { describe, expect, it, vi } from "bun:test";
 import { resolvePredicateTimeout } from "@oh-my-pi/pi-coding-agent/tools/browser/run-cancellation";
 import {
 	dispatchScroll,
@@ -55,6 +55,19 @@ describe("browser scroll acknowledgement", () => {
 			"target closed",
 		);
 	});
+
+	it("cancels the acknowledgement deadline after a prompt dispatch", async () => {
+		vi.useFakeTimers();
+		try {
+			const timerCount = vi.getTimerCount();
+
+			await dispatchScroll(() => Promise.resolve());
+
+			expect(vi.getTimerCount()).toBe(timerCount);
+		} finally {
+			vi.useRealTimers();
+		}
+	});
 });
 
 describe("browser wait-helper timeout resolution", () => {