fix(remote): resolve service names against the remote server

Remote mode resolved names with the local alias table and built an empty stub for any unknown tag, so an unentitled service showed a blank help page. Resolve against the server's tags and aliases, and reject unknown names with the list the server does offer.

tests/remote/unit/test_remote_command_unknown_tag.py

@@ -0,0 +1,51 @@
+"""make_remote_command resolves names against the remote server's list and reports the failures."""
+
+from __future__ import annotations
+
+from unittest.mock import patch
+
+import click
+import pytest
+
+from unshackle.core.services import Services
+
+SERVED = [
+    {"tag": "AMZN", "url": "https://example.com", "help": "Amazon.", "cli_params": [], "aliases": []},
+    {"tag": "HMAX", "url": "https://example.com", "help": "Max.", "cli_params": [], "aliases": ["MAX", "hbomax"]},
+]
+
+
+def _make(name: str) -> click.Command:
+    return Services.make_remote_command(name, ctx=click.Context(click.Command("dl")))
+
+
+def test_unknown_name_raises_with_typed_name_and_available_list() -> None:
+    with patch.object(Services, "fetch_remote_services", return_value=SERVED):
+        with pytest.raises(click.ClickException, match=r"does not offer a service named 'BBC'.*AMZN, HMAX"):
+            _make("BBC")
+
+
+def test_served_tag_builds_full_command() -> None:
+    with patch.object(Services, "fetch_remote_services", return_value=SERVED):
+        cmd = _make("AMZN")
+    assert cmd.help == "Amazon."
+
+
+def test_server_alias_resolves_to_server_tag() -> None:
+    with patch.object(Services, "fetch_remote_services", return_value=SERVED):
+        cmd = _make("max")
+    assert cmd.name == "HMAX"
+    assert cmd.help == "Max."
+
+
+def test_empty_service_list_raises_no_services_message() -> None:
+    with patch.object(Services, "fetch_remote_services", return_value=[]):
+        with pytest.raises(click.ClickException, match=r"offers no services to your API key"):
+            _make("AMZN")
+
+
+def test_fetch_failure_keeps_stub_instead_of_raising() -> None:
+    with patch.object(Services, "fetch_remote_services", return_value=None):
+        cmd = _make("AMZN")
+    assert cmd.name == "AMZN"
+    assert cmd.help is None