Let a config-only command work on no database

`settings` and `download-models` read the configuration and open nothing, but
resolved a scope to be constructed, so `--db-name nope` failed them over a
selection they never use. `HaikuRAGApp` takes no scope for those, and asking it
for one is an error rather than a silent default.

haiku_rag_slim/haiku/rag/app.py

@@ -35,16 +35,25 @@ logger = logging.getLogger(__name__)
 class HaikuRAGApp:
     def __init__(
         self,
-        scope: "DatabaseScope",
+        scope: "DatabaseScope | None" = None,
         config: AppConfig | None = None,
         read_only: bool = False,
     ):
-        """The databases this command works on, resolved by whoever built it."""
-        self.scope = scope
+        """The databases this command works on, resolved by whoever built it.
+
+        `scope` is None for configuration-only commands.
+        """
+        self._scope = scope
         self.config = config if config is not None else get_config()
         self.read_only = read_only
         self.console = Console()
 
+    @property
+    def scope(self) -> "DatabaseScope":
+        """The databases this command works on."""
+        assert self._scope is not None, "this command works on no database"
+        return self._scope
+
     @property
     def _one(self) -> "DatabaseRef":
         """The one database this command works on.

haiku_rag_slim/haiku/rag/cli.py

@@ -461,9 +461,7 @@ def settings():
 
     config = get_config()
     # Neither of these opens a database; the scope is whatever is configured.
-    app = HaikuRAGApp(
-        scope=resolve_scope(covers_set=True), config=config, read_only=True
-    )
+    app = HaikuRAGApp(config=config, read_only=True)
     app.show_settings()
 
 
@@ -781,9 +779,7 @@ def tag_restore(
 def download_models_cmd():
     from haiku.rag.app import HaikuRAGApp
 
-    app = HaikuRAGApp(
-        scope=resolve_scope(covers_set=True), config=get_config(), read_only=True
-    )
+    app = HaikuRAGApp(config=get_config(), read_only=True)
     try:
         asyncio.run(app.download_models())
     except Exception as e:

tests/test_cli.py

@@ -326,6 +326,50 @@ class TestSelectingADatabaseByName:
         assert cli_module._db_name is None
 
 
+class TestCommandsThatWorkOnNoDatabase:
+    """`settings` and `download-models` read the configuration. A name that
+    selects a database is nothing to them, including a wrong one."""
+
+    def test_settings_ignores_an_unknown_name(self, tmp_path, monkeypatch):
+        import haiku.rag.config as config_module
+
+        monkeypatch.setattr(config_module, "_config", None)
+        config_file = tmp_path / "haiku.rag.yaml"
+        config_file.write_text("lancedb:\n  databases:\n    alpha: /data/a.lancedb\n")
+
+        result = runner.invoke(
+            cli, ["--config", str(config_file), "--db-name", "nope", "settings"]
+        )
+
+        assert result.exit_code == 0, result.output
+        assert "haiku.rag configuration" in result.output
+
+    def test_download_models_ignores_an_unknown_name(self, tmp_path, monkeypatch):
+        import haiku.rag.config as config_module
+
+        monkeypatch.setattr(config_module, "_config", None)
+        config_file = tmp_path / "haiku.rag.yaml"
+        config_file.write_text("lancedb:\n  databases:\n    alpha: /data/a.lancedb\n")
+        downloaded: list[object] = []
+
+        async def nothing_to_download(config):
+            downloaded.append(config)
+            return
+            yield  # pragma: no cover - an empty async generator needs one
+
+        monkeypatch.setattr(
+            "haiku.rag.client.downloads.download_models", nothing_to_download
+        )
+
+        result = runner.invoke(
+            cli,
+            ["--config", str(config_file), "--db-name", "nope", "download-models"],
+        )
+
+        assert result.exit_code == 0, result.output
+        assert len(downloaded) == 1
+
+
 class TestResolvingTheDatabasePath:
     def test_a_path_wins_when_nothing_is_selected(self, monkeypatch):
         monkeypatch.setattr("haiku.rag.cli._db_name", None)