fix(models): stop reporting errored downloads as still downloading (#926)

TaskManager.error_download() intentionally keeps a failed task in the
active list (status="error") so /tasks/active can surface the error
and retry UI — but /models/status derived its "downloading" flag from
the same unfiltered list. One failed download therefore showed the
model as downloading:true / downloaded:false for the life of the
process, masking the model's real cache state (even a fully valid
on-disk cache) until an app restart. Likely behind endless-spinner
reports like #181 and the restart-fixes-it pattern in #883.

Add TaskManager.get_pending_downloads() (downloading/extracting only)
and use it in /models/status; /tasks/active behavior is unchanged.

Fixes #925


Claude-Session: https://claude.ai/code/session_011iwL9AyeAWgz2jpgcHxJpC

Co-authored-by: Claude Fable 5 <[email protected]>

backend/routes/models.py

@@ -231,7 +231,10 @@ async def get_model_status():
     backend_type = get_backend_type()
     task_manager = get_task_manager()
 
-    active_download_names = {task.model_name for task in task_manager.get_active_downloads()}
+    # Pending only — an errored task stays in the active list for the
+    # error/retry UI, but reporting it as "downloading" here would mask
+    # the model's real cache state until the app restarts (issue #925).
+    active_download_names = {task.model_name for task in task_manager.get_pending_downloads()}
 
     try:
         from huggingface_hub import scan_cache_dir