fix(remote): stop warning about missing keys for tracks that carry no DRM

The server names the clear tracks in the licence response and the client skips them instead of warning for every requested track without keys.

tests/remote/unit/test_server_cdm_key_verification.py

@@ -146,3 +146,25 @@ async def test_server_tells_a_remote_vault_only_when_it_served_the_pair(monkeypa
     assert local.flagged == [("SVC", KID, "v", "sqlite")]
     assert source.flagged == [("SVC", KID, "v", "sqlite")]
     assert bystander.flagged == []
+
+
+def test_resolve_server_keys_does_not_warn_for_clear_tracks(monkeypatch):
+    """A requested track the server lists in clear_tracks carries no DRM, so its
+    missing keys are expected and draw no warning."""
+    svc = remote_service()
+    warnings: list = []
+    svc.log = SimpleNamespace(warning=lambda msg, *a, **k: warnings.append(msg), debug=lambda *a, **k: None)
+    svc._server_cdm = True
+    svc.drain_server_logs = lambda: None
+    svc.client = SimpleNamespace(post=lambda ep, data: {"keys": {}, "clear_tracks": ["a-1"]})
+
+    video_track = SimpleNamespace(id="v-1", drm=None)
+    audio_track = SimpleNamespace(id="a-1", drm=None)
+
+    class Tracks(list):
+        videos = [video_track]
+        audio = [audio_track]
+
+    svc.resolve_server_keys(SimpleNamespace(tracks=Tracks([video_track, audio_track])))
+
+    assert warnings == ["Server CDM returned no content keys for track v-1"]