Let queued and player extensions use the full duration slider.

Stop clamping extensions to 3s or 5s so each segment can use the same length control as generate.

server/api/extend.post.ts

@@ -6,7 +6,8 @@ const SCHEDULERS = new Set(['simple', 'ddim_uniform', 'sgm_uniform'])
 
 function parseExtendDuration(raw: unknown) {
   const seconds = Number(raw)
-  return seconds === 3 || seconds === 5 ? seconds : 5
+  if (!Number.isFinite(seconds)) return 5
+  return Math.min(120, Math.max(0.5, Math.round(seconds * 10) / 10))
 }
 
 function frameLength(seconds: number, fps: number) {