make done plans terminal, add ffprobe preflight to skip already-processed files

root cause of duplicate pipeline entries: rescan.ts flipped done plans
back to pending whenever a post-job jellyfin refresh returned stale
metadata, putting the item back in review and letting a second jobs row
pile up in done. done is now sticky across rescans (error still
re-opens for retries).

second line of defense: before spawning ffmpeg, ffprobe the file and
compare audio count/language/codec order + embedded subtitle count
against the plan. if it already matches, mark the job done with the
reason in jobs.output and skip the spawn. prevents corrupting a
post-processed file with a stale stream-index command.

server/api/execute.ts

@@ -16,6 +16,7 @@ import {
 	waitForProcessWindow,
 } from "../services/scheduler";
 import { loadLibrary as loadSonarrLibrary, isUsable as sonarrUsable } from "../services/sonarr";
+import { verifyDesiredState } from "../services/verify";
 import type { Job, MediaItem, MediaStream } from "../types";
 
 function parseLanguageList(raw: string | null | undefined, fallback: string[]): string[] {
@@ -403,6 +404,31 @@ async function runJob(job: Job): Promise<void> {
 			db.prepare("UPDATE review_plans SET status = 'error' WHERE item_id = ?").run(job.item_id);
 			return;
 		}
+
+		// Preflight: if the file already matches the plan, skip ffmpeg. Cheap
+		// guard against re-running a stream-index-based command against a file
+		// that's already been processed — which would either error out or
+		// silently corrupt the file.
+		try {
+			const verify = await verifyDesiredState(db, job.item_id, itemRow.file_path);
+			if (verify.matches) {
+				const msg = `Preflight check: ${verify.reason}\nSkipping FFmpeg — no work needed.`;
+				log(`Job ${job.id} ${msg.replace(/\n/g, " ")}`);
+				db.transaction(() => {
+					db
+						.prepare(
+							"UPDATE jobs SET status = 'done', exit_code = 0, output = ?, completed_at = datetime('now') WHERE id = ?",
+						)
+						.run(msg, job.id);
+					db.prepare("UPDATE review_plans SET status = 'done' WHERE item_id = ?").run(job.item_id);
+				})();
+				emitJobUpdate(job.id, "done", msg);
+				return;
+			}
+			log(`Job ${job.id} preflight: ${verify.reason} — running FFmpeg`);
+		} catch (err) {
+			warn(`Job ${job.id} preflight check errored: ${String(err)} — proceeding with FFmpeg`);
+		}
 	}
 
 	emitJobUpdate(job.id, "running");