test: add tests for copilot ACP deprecation detection and Azure URL mapping

Cover the deprecation pattern matching against real gh-copilot stderr
output, verify the GitHub Models Azure URL is in _URL_TO_PROVIDER, and
confirm _is_github_models_base_url recognises the Azure endpoint.

tests/agent/test_copilot_acp_deprecation.py

@@ -0,0 +1,59 @@
+"""Tests for gh-copilot CLI deprecation detection and GitHub Models Azure URL mapping."""
+
+import pytest
+
+from agent.copilot_acp_client import _DEPRECATION_PATTERNS
+
+
+class TestDeprecationPatternDetection:
+    """Verify that stderr messages from a deprecated gh-copilot CLI are caught."""
+
+    _REAL_DEPRECATION_STDERR = (
+        "The gh-copilot extension has been deprecated in favor of the newer "
+        "GitHub Copilot CLI.\nFor more information, visit:\n"
+        "- Copilot CLI: https://github.com/github/copilot-cli\n"
+        "- Deprecation announcement: https://github.blog/changelog/"
+        "2025-09-25-upcoming-deprecation-of-gh-copilot-cli-extension\n"
+        "No commands will be executed."
+    )
+
+    def test_real_deprecation_message_matches(self):
+        lower = self._REAL_DEPRECATION_STDERR.lower()
+        assert any(pat in lower for pat in _DEPRECATION_PATTERNS)
+
+    @pytest.mark.parametrize(
+        "stderr_line",
+        [
+            "The gh-copilot extension has been deprecated",
+            "No commands will be executed.",
+            "See deprecation notice at ...",
+            "Install copilot-cli instead",
+        ],
+    )
+    def test_individual_patterns_match(self, stderr_line: str):
+        lower = stderr_line.lower()
+        assert any(pat in lower for pat in _DEPRECATION_PATTERNS)
+
+    def test_normal_stderr_does_not_match(self):
+        normal = "Error: connection refused"
+        assert not any(pat in normal.lower() for pat in _DEPRECATION_PATTERNS)
+
+
+class TestGitHubModelsAzureUrl:
+    """Verify that the Azure GitHub Models URL is recognised."""
+
+    def test_url_to_provider_contains_azure_models(self):
+        from agent.model_metadata import _URL_TO_PROVIDER
+
+        assert _URL_TO_PROVIDER.get("models.inference.ai.azure.com") == "github-models"
+
+    def test_is_github_models_base_url_recognises_azure(self):
+        from hermes_cli.models import _is_github_models_base_url
+
+        assert _is_github_models_base_url("https://models.inference.ai.azure.com")
+        assert _is_github_models_base_url("https://models.inference.ai.azure.com/v1/chat")
+
+    def test_is_github_models_base_url_still_recognises_github_ai(self):
+        from hermes_cli.models import _is_github_models_base_url
+
+        assert _is_github_models_base_url("https://models.github.ai/inference")