core/cli: /models and remote catalog for model selection

Cache GET /models, merge with config ids for Tab and choose; free-form model ids allowed.

tests/test_cli/test_models_source.py

@@ -0,0 +1,52 @@
+from __future__ import annotations
+
+import pytest
+
+from plyngent.cli.models_source import (
+    client_supports_models,
+    config_model_ids,
+    fetch_remote_model_ids,
+    merge_model_choices,
+    model_choices_for_provider,
+)
+from plyngent.config.models import ModelConfig, OpenAICompatibleProvider
+
+
+def test_merge_model_choices_union() -> None:
+    assert merge_model_choices(["b", "a"], ["a", "c"]) == ["a", "b", "c"]
+    assert merge_model_choices(["a"], None) == ["a"]
+    assert merge_model_choices([], ["z"]) == ["z"]
+
+
+def test_model_choices_for_provider() -> None:
+    provider = OpenAICompatibleProvider(
+        access_key_or_token="sk",
+        url="https://x/v1",
+        models={"cfg": ModelConfig()},
+    )
+    assert config_model_ids(provider) == ["cfg"]
+    assert model_choices_for_provider(provider, remote_ids=["remote", "cfg"]) == ["cfg", "remote"]
+
+
+def test_client_supports_models() -> None:
+    class Ok:
+        async def models(self) -> list[str]:
+            return ["m"]
+
+    class No:
+        pass
+
+    assert client_supports_models(Ok())
+    assert not client_supports_models(No())
+
+
+@pytest.mark.asyncio
+async def test_fetch_remote_model_ids() -> None:
+    class Ok:
+        async def models(self) -> list[str]:
+            return ["z", "a"]
+
+    assert await fetch_remote_model_ids(Ok()) == ["z", "a"]
+
+    with pytest.raises(TypeError, match="does not support"):
+        _ = await fetch_remote_model_ids(object())

tests/test_cli/test_repl_commands.py

@@ -235,7 +235,7 @@ async def test_provider_switch_prompts_when_model_missing(
     # When switching to b, only-a is missing → select_model is invoked interactively.
     monkeypatch.setattr(
         "plyngent.cli.slash.select_model",
-        lambda provider, preferred=None, interactive=True: "only-b",
+        lambda provider, preferred=None, interactive=True, choices=None: "only-b",
     )
     assert await handle_slash(state, "/provider b") is True
     assert state.provider_name == "b"

tests/test_cli/test_selection.py

@@ -64,11 +64,25 @@ def test_select_provider_interactive_choose() -> None:
     assert name == "b"
 
 
-def test_select_model_when_preferred_missing_raises() -> None:
+def test_select_model_preferred_not_in_config_allowed() -> None:
+    """Explicit model ids are accepted; the API validates at chat time."""
     provider = OpenAICompatibleProvider(
         access_key_or_token="sk",
         url="https://x/v1",
         models={"m1": ModelConfig()},
     )
-    with pytest.raises(Exception, match="unknown model"):
-        _ = select_model(provider, preferred="nope")
+    assert select_model(provider, preferred="nope") == "nope"
+    assert select_model(provider, preferred="  custom  ") == "custom"
+
+
+def test_select_model_choices_override() -> None:
+    from plyngent.prompting import temporary_backend
+    from tests.test_prompting import ScriptedBackend
+
+    provider = OpenAICompatibleProvider(
+        access_key_or_token="sk",
+        url="https://x/v1",
+        models={"m1": ModelConfig()},
+    )
+    with temporary_backend(ScriptedBackend(["remote-x"])):
+        assert select_model(provider, choices=["remote-x", "m1"]) == "remote-x"