fix(coding-agent): stabilized browser worker startup

Gave browser worker initialization an infrastructure timeout floor so short navigation budgets do not expire before a loaded runner starts the worker.

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

@@ -134,6 +134,7 @@ const tabs = new Map<string, TabSession>();
 // awaits) cannot interleave and leak a worker + browser refCount.
 const acquireChains = new Map<string, Promise<void>>();
 const GRACE_MS = 750;
+const WORKER_INIT_TIMEOUT_MS = 15_000;
 // Names of tabs the supervisor force-killed (timeout past grace, failed recycle),
 // mapped to the kill reason. Lets the next `run` on that name explain WHY the tab
 // vanished instead of a bare "not alive". Cleared when the name is opened again.
@@ -272,7 +273,11 @@ async function acquireTabImpl(
 	}
 	let info: ReadyInfo;
 	try {
-		info = await initializeTabWorker(worker, initPayload, opts.timeoutMs + GRACE_MS);
+		info = await initializeTabWorker(
+			worker,
+			initPayload,
+			Math.max(WORKER_INIT_TIMEOUT_MS, opts.timeoutMs + GRACE_MS),
+		);
 	} catch (error) {
 		// `BuildMessage`-class failures arrive asynchronously via the worker's `error` event,
 		// after `spawnTabWorker`'s synchronous try/catch has already returned. Fall back to
@@ -287,7 +292,11 @@ async function acquireTabImpl(
 		});
 		worker = await spawnInlineWorker();
 		try {
-			info = await initializeTabWorker(worker, initPayload, opts.timeoutMs + GRACE_MS);
+			info = await initializeTabWorker(
+				worker,
+				initPayload,
+				Math.max(WORKER_INIT_TIMEOUT_MS, opts.timeoutMs + GRACE_MS),
+			);
 		} catch (inlineError) {
 			await worker.terminate().catch(() => undefined);
 			if (tempHold || browser.refCount === 0) await releaseBrowser(browser, { kill: false });