fix: clarify AI generation failure retry states

app/gui/workers.py

@@ -4,7 +4,7 @@ from __future__ import annotations
 
 from .widgets import *
 class GenerateWorker(BaseWorker):
-    """Generate titles and covers for collected tasks."""
+    """Generate titles and covers for eligible collected or failed generation tasks."""
 
     def __init__(
         self,
@@ -39,7 +39,7 @@ class GenerateWorker(BaseWorker):
         self._account_by_alias = account_by_alias
         eligible = [
             task for task in self.tasks
-            if getattr(task, "stage", None) == "collected"
+            if ai.is_generatable_task(task)
         ]
         self._eligible_total = len(eligible)
         self._task_positions = {