Implement Apex Agent MVP scaffold

core/errors.py

@@ -0,0 +1,30 @@
+from __future__ import annotations
+
+
+class ApexAgentError(Exception):
+    """Base error for semantic errors surfaced above the driver layer."""
+
+
+class DriverError(ApexAgentError):
+    """A driver operation failed."""
+
+
+class DeviceNotFoundError(ApexAgentError):
+    """A requested device id is unknown."""
+
+
+class DeviceOfflineError(ApexAgentError):
+    """A device is unavailable or lost its connection."""
+
+
+class DeviceBusyError(ApexAgentError):
+    """A device is already in use."""
+
+
+class ElementNotFoundError(ApexAgentError):
+    """A requested screen element was not found."""
+
+
+class TaskFailedError(ApexAgentError):
+    """A task failed before reaching its goal."""
+