Honor return annotations of async pytest fixtures

Async fixtures skipped the annotation branch, so a `-> T` annotation was
ignored and only the body was inferred. Infer the annotation directly:
the awaited value for coroutines, and the yielded value for annotated
async generators. Add cases where the body is not inferable.

Also drop the tooling note from the AUTHORS entry.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

test/completion/pytest.py

@@ -1,4 +1,4 @@
-from typing import Generator
+from typing import AsyncGenerator, Generator
 
 import pytest
 from pytest import fixture
@@ -229,6 +229,16 @@ async def async_yield_fixture():
     yield 1.0
 
 
+@pytest.fixture
+async def async_annotated_opaque() -> int:
+    return opaque_value
+
+
+@pytest.fixture
+async def async_generator_annotated() -> AsyncGenerator[str, None]:
+    yield opaque_value
+
+
 #? ['async_fixture']
 def test_async_fixture_completion(async_fixt
     pass
@@ -243,6 +253,13 @@ def test_async_fixture_inference(async_fixture, async_annotated_fixture, async_y
     async_yield_fixture
 
 
+def test_async_fixture_annotation(async_annotated_opaque, async_generator_annotated):
+    #? int()
+    async_annotated_opaque
+    #? str()
+    async_generator_annotated
+
+
 #! 30 ['def async_fixture']
 def test_async_fixture_goto(async_fixture):
     pass