Fix frozenset error in clear_cache

The repos attribute from scan_cache_dir() is a frozenset, not a list,
so .pop() doesn't work. Fixed by using next(iter()) instead.

videogen.py

@@ -868,8 +868,8 @@ def clear_cache(yes=False):
         else:
             print("  ⚠️  Auto-confirming cache clear due to --yes flag")
         
-        # Get cache directory path
-        cache_dir = cache_info.repos.pop().repo_path.parent
+        # Get cache directory path (repos is a frozenset, so use next() to get one item)
+        cache_dir = next(iter(cache_info.repos)).repo_path.parent
         
         # Delete all cache contents
         for item in cache_dir.iterdir():