fix: address CodeRabbit review feedback (round 2)

- Reorder recorder.stop() before cleanupCapturedMedia to avoid dropping final chunk (recordingStopHelpers)
- Guard speed region divisor against 0/NaN/Infinity (audioEncoder shared)

src/hooks/useScreenRecorder/recordingStopHelpers.ts

@@ -88,8 +88,8 @@ export async function stopBrowserRecordingSession(options: StopRecordingOptions)
 	}
 
 	options.refs.pendingWebcamPathPromise.current = stopWebcamRecorder(options.refs);
-	await options.cleanupCapturedMedia();
 	recorder.stop();
+	await options.cleanupCapturedMedia();
 	options.setRecording(false);
 	window.electronAPI?.setRecordingState(false);
 	return true;

src/lib/exporter/audioEncoder/shared.ts

@@ -123,10 +123,12 @@ export function buildTimelineSlices(
 			(s) => midpoint >= s.startMs && midpoint < s.endMs,
 		);
 
+		const rawSpeed = speedRegion?.speed ?? 1;
+		const speed = Number.isFinite(rawSpeed) && rawSpeed > 0 ? rawSpeed : 1;
 		slices.push({
 			sourceStartMs: start,
 			sourceEndMs: end,
-			speed: speedRegion?.speed ?? 1,
+			speed,
 		});
 	}