sar3d: GPU port of the notebook with four views

The sar3d processor is rewritten as a checked port of Multi_antenna_3D_clean_v1.ipynb:
NVRTC kernels, timing from the trace stamps, notebook parameter names and one cubic
SAR_VOXEL_M. It adds front, side, top and 3D views, drops gpr_cpp and the parity tools,
and the GUI speed now applies only while the socket speed is ignored.

python_app/hardware_full/laser_control/protocol.py

@@ -4,6 +4,7 @@ Encodes commands to wire bytes, decodes device responses, and manages the
 serial port connection to the laser control board.
 """
 
+import errno
 import logging
 import struct
 from typing import Optional
@@ -204,9 +205,9 @@ class Protocol:
                 exclusive=True,
             )
         except serial.SerialException as exc:
-            # pyserial raises SerialException with errno EAGAIN/EWOULDBLOCK (11)
-            # when another process already holds the exclusive flock.
-            if getattr(exc, "errno", None) in (11,) or "exclusively lock" in str(exc).lower():
+            # pyserial raises SerialException with errno EWOULDBLOCK when another
+            # process already holds the exclusive flock.
+            if getattr(exc, "errno", None) == errno.EWOULDBLOCK or "exclusively lock" in str(exc).lower():
                 logger.error("Laser serial port '%s' is busy (held by another program)", port)
                 raise PortBusyError(port) from exc
             logger.error("Cannot open laser serial port '%s': %s", port, exc)