Stop ghost extension clips and recover last-frame extract after an interrupt.

Only one Comfy finish path can save a clip, hide catalog entries whose MP4 is missing, and retry last-frame extract so a truncated file does not dump FFmpeg noise into the UI.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/utils/jobs.ts

@@ -78,6 +78,8 @@ export interface Job {
   }
   error?: string
   socketReady?: boolean
+  saving?: boolean
+  savedPromptId?: string
   segmentBuffer?: Buffer
   events: JobEvent[]
   listeners: Set<(event: JobEvent) => void>