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_last_login.py

@@ -100,7 +100,12 @@ def test_the_admin_user_list_carries_last_login(as_user, db, make_user):
 def test_the_account_sees_its_own_last_sign_in(client, db, make_user):
     # Settings → Account shows it (prod UAT 2026-09-19: only the admin's user list did).
     make_user(email="me@example.com", password=_PW)
-    client.post("/auth/password-login", json={"email": "me@example.com", "password": _PW})
+    assert (
+        client.post(
+            "/auth/password-login", json={"email": "me@example.com", "password": _PW}
+        ).status_code
+        == 200
+    )
 
     stamp = client.get("/api/me").json()["last_login_at"]