Refactor DDM backend to use monitorcontrol for input switching and update error messages for clarity

app/service.py

@@ -122,9 +122,9 @@ class KvmSwitcherService:
             ddm_slot is not None or supports_monitor_targeting
         )
         if not self.ddm_backend.is_available():
-            errors.append("DDM.exe was not found.")
+            errors.append("Alienware monitorcontrol backend is not ready.")
         elif ddm_slot is None and not supports_monitor_targeting:
-            errors.append("Alienware DDM slot could not be resolved.")
+            errors.append("Alienware monitorcontrol target could not be resolved.")
 
         trigger_target_port = self._port_name_for_input_code(scan.trigger_input_code)
         desired_port = self._resolve_desired_port(config, scan)
@@ -279,7 +279,7 @@ class KvmSwitcherService:
                 return "waiting_for_trigger_match", last_switch_at, scan, errors
             if verify_scan.alienware_input_code is None:
                 errors.append(
-                    "Alienware input could not be read after switch; assuming success because DDM command completed."
+                    "Alienware input could not be read after switch; assuming success because switch command completed."
                 )
                 self._samsung_session_successful = True
                 return "switched_unverified", last_switch_at, scan, errors
@@ -307,7 +307,7 @@ def _is_blocking_error(error: str) -> bool:
     normalized = error.strip()
     non_blocking_prefixes = (
         "Unable to read Alienware target monitor input source:",
-        "Alienware input could not be read after switch; assuming success because DDM command completed.",
+        "Alienware input could not be read after switch; assuming success because switch command completed.",
         "Samsung trigger monitor did not expose a Samsung model in DDC/CI; using the only non-Alienware DDC monitor as trigger.",
     )
     return not any(normalized.startswith(prefix) for prefix in non_blocking_prefixes)