feat: add provider-neutral tracker automation

tests/test_provider_resolution.py

@@ -0,0 +1,37 @@
+import unittest
+
+from tracker import TrackerError, resolve_provider  # type: ignore[reportMissingImports]
+
+
+class ProviderResolutionTests(unittest.TestCase):
+    def test_cli_provider_wins_over_environment_and_remote(self):
+        self.assertEqual(
+            resolve_provider(
+                explicit="github",
+                env={"TRACKER_PROVIDER": "gitlab"},
+                remote="https://gitea.example.com/team/repo.git",
+            ),
+            "github",
+        )
+
+    def test_environment_provider_wins_over_remote(self):
+        self.assertEqual(
+            resolve_provider(
+                env={"TRACKER_PROVIDER": "gitlab"},
+                remote="git@github.com:team/repo.git",
+            ),
+            "gitlab",
+        )
+
+    def test_remote_provider_is_detected(self):
+        self.assertEqual(resolve_provider(remote="git@gitea.example.com:team/repo.git"), "gitea")
+
+    def test_unsupported_remote_is_structured_error(self):
+        with self.assertRaises(TrackerError) as context:
+            resolve_provider(remote="https://example.com/team/repo.git")
+        self.assertEqual(context.exception.code, "provider_detection_failed")
+        self.assertFalse(context.exception.retryable)
+
+
+if __name__ == "__main__":
+    unittest.main()