abort queue loop when auto-process-queue is disabled

The toggle's disable branch only wrote the config, leaving runSequential
draining indefinitely — its loop only checked signal.aborted, and the
drain re-fetch at the bottom kept pulling new pending jobs.

Add stopQueueProcessor() (mirrors stopAutoProcessLoop for the inbox
sorter) and call it from the disable branch. Current ffmpeg job runs
to completion; no new jobs start. Use POST /stop for a hard kill.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/api/execute.ts

@@ -183,6 +183,19 @@ export function maybeStartQueueProcessor(): boolean {
 	return true;
 }
 
+/**
+ * Abort the queue loop so no more jobs start after the current one. The
+ * currently running ffmpeg keeps going — use POST /stop to also kill it.
+ * Mirrors stopAutoProcessLoop() for the inbox sorter.
+ */
+export function stopQueueProcessor(): boolean {
+	if (queueAbort) {
+		queueAbort.abort();
+		return true;
+	}
+	return false;
+}
+
 /** Parse "Duration: HH:MM:SS.MS" from ffmpeg startup output. */
 function parseFFmpegDuration(line: string): number | null {
 	const match = line.match(/Duration:\s*(\d+):(\d+):(\d+)\.(\d+)/);