fix(export): address remaining PR #295 review threads

- Include `resolvedWebcamVideoUrl` in the dependency arrays for
  `captureProjectThumbnail` and `handleExport` so thumbnail capture and
  export settings stay in sync when the webcam URL refreshes.
- Clear `VideoMuxer.streamSink` before awaiting `closeIpcExportStream`
  in `finalize()` to close the race where a concurrent `destroy()` →
  `abortStream()` could try to close the same stream ID a second time.

src/components/video-editor/VideoEditor.tsx

@@ -946,6 +946,7 @@ export default function VideoEditor() {
 		cursorTelemetry,
 		clipRegions,
 		padding,
+		resolvedWebcamVideoUrl,
 		shadowIntensity,
 		showCursor,
 		speedRegions,
@@ -4356,6 +4357,7 @@ export default function VideoEditor() {
 			padding,
 			cropRegion,
 			webcam,
+			resolvedWebcamVideoUrl,
 			annotationRegions,
 			autoCaptions,
 			autoCaptionSettings,

src/lib/exporter/muxer.ts

@@ -172,8 +172,11 @@ export class VideoMuxer {
 			if (!sink) {
 				throw new Error("Stream target closed before finalization");
 			}
-			const closeResult = await closeIpcExportStream(sink.streamId);
+			// Clear streamSink before awaiting close so a concurrent destroy()→
+			// abortStream() short-circuits on `!this.streamSink` instead of racing
+			// us for the same streamId.
 			this.streamSink = null;
+			const closeResult = await closeIpcExportStream(sink.streamId);
 			return {
 				mode: "stream",
 				tempFilePath: closeResult.tempPath,