Enforce strict Pyright gate

src/docforge/rendering.py

@@ -6,7 +6,7 @@ import fcntl
 import hashlib
 import os
 import tempfile
-from collections.abc import Callable, Iterator
+from collections.abc import Callable, Generator
 from contextlib import contextmanager
 from pathlib import Path
 
@@ -279,7 +279,7 @@ class RenderService:
         }
 
     @contextmanager
-    def _lock(self) -> Iterator[None]:
+    def _lock(self) -> Generator[None]:
         root = self.project.descriptor.cache_root
         if root.resolve(strict=False) != root:
             raise DocForgeError("path_escape", "Render lock directory is not safe")