Add MX-T40 BLE desktop controller and protocol documentation

tests/test_imports.py

@@ -0,0 +1,23 @@
+"""The protocol and CLI must remain usable on machines without a display."""
+
+import subprocess
+import sys
+import unittest
+
+
+class ImportTests(unittest.TestCase):
+    def test_headless_import_and_help(self):
+        script = """
+import sys
+from controller import protocol, session, messages, cli
+assert 'tkinter' not in sys.modules
+assert 'bleak' not in sys.modules
+try:
+    cli.main(['--help'])
+except SystemExit as exc:
+    assert exc.code == 0
+assert 'tkinter' not in sys.modules
+"""
+        result = subprocess.run([sys.executable, "-c", script], capture_output=True, text=True)
+        self.assertEqual(result.returncode, 0, result.stderr)
+        self.assertIn("--transport", result.stdout)