test: no test throws a response away; the stream session is narrowed, not baselined

The 7 baselined Optional accesses in plex/stream.py were one fact the type did not carry: the
initial spawn (replace_only=None) always supersedes, so only the fallback respawn can get None.
An assert at the call site says so; the pyright baseline drops 195 -> 188.

test_abuse_limits: the public-URL and YouTube enqueue tests stopped at the profile lookup
(400 no_profile) and passed on that unrelated refusal. They now send an inline spec and assert
the job is queued. The same shape — a request whose response is discarded — sat at 53 more
places across the suite (all returned what they should, measured with a TestClient probe);
each now asserts its status, and test_response_checked keeps it that way (seen red).

backend/tests/test_plex_playlist_add_positions.py

@@ -105,8 +105,11 @@ def test_remove_then_put_back_is_no_change(db, make_user, as_user):
     user = make_user()
     pl = _seed(db, user, ["a", "b", "c", "d"], extra=())
     client = as_user(user)
-    client.post(
-        f"/api/plex/playlists/{pl.id}/items/remove-bulk", json={"item_rating_keys": ["b", "d"]}
+    assert (
+        client.post(
+            f"/api/plex/playlists/{pl.id}/items/remove-bulk", json={"item_rating_keys": ["b", "d"]}
+        ).status_code
+        == 200
     )
     assert _order(db, pl.id)[0] == ["a", "c"]
     _add(client, pl.id, ["b", "d"], [1, 3])