feat(serialcomm): implement stream auto-detection, fallback baudrate, and virtual port discovery

- Add automatic format detection (binary, ASCII hex dump, or text line) in StreamReader based on stream preambles.
- Implement fallback to 115200 baudrate when 888888 ioctl fails (critical for macOS PTYs).
- Parse binary streams (X family) with little-endian sequence/length headers and Modbus CRC-16 checks.
- Discover and prioritize virtual serial ports (from running socat instances) in enumerate_ports using lsof.
- Update FakeTransport to mock read() and readline() calls for unit test compatibility.

src/pygui/serialcomm/device_service.py

@@ -37,7 +37,58 @@ class DeviceService:
 
     def enumerate_ports(self) -> list[str]:
         """Return list of available serial port names."""
-        return [p.device for p in serial.tools.list_ports.comports()]
+        hardware_ports = [p.device for p in serial.tools.list_ports.comports()]
+        virtual_ports = []
+
+        # On macOS/Linux, also detect virtual loopback serial ports (PTYs) opened by socat
+        import platform
+        import subprocess
+        import re
+
+        if platform.system() in ("Darwin", "Linux"):
+            try:
+                # Find PTYs opened by socat
+                result = subprocess.run(
+                    ["lsof", "-c", "socat"],
+                    capture_output=True,
+                    text=True,
+                    check=False
+                )
+                if result.returncode == 0:
+                    for line in result.stdout.splitlines():
+                        parts = line.strip().split()
+                        if len(parts) >= 9:
+                            fd = parts[3]
+                            # Exclude standard FDs (0, 1, 2) which are typically the controlling terminal
+                            if fd.startswith(('0', '1', '2')):
+                                continue
+                            name = parts[-1]
+                            match = re.search(r'(/dev/(?:ttys\d+|pts/\d+))\b', name)
+                            if match:
+                                port = match.group(1)
+                                if port not in virtual_ports:
+                                    virtual_ports.append(port)
+            except Exception as e:
+                log.debug("Error listing virtual ports via lsof: %s", e)
+
+        # Prioritize physical USB serial interfaces first -> generic hardware -> virtual ports
+        # Virtual ports (PTYs detected via lsof) should NOT appear in hardware_ports,
+        # so we filter them out explicitly.
+        virtual_set = set(virtual_ports)
+        ordered_ports = []
+        for p in hardware_ports:
+            if "usbserial" in p.lower() or "usb" in p.lower() or "ttyusb" in p.lower():
+                if p not in ordered_ports:
+                    ordered_ports.append(p)
+        for p in hardware_ports:
+            if p not in ordered_ports and p not in virtual_set:
+                ordered_ports.append(p)
+        for p in virtual_ports:
+            if p not in ordered_ports:
+                ordered_ports.append(p)
+
+        return ordered_ports
+
 
     def detect_wafer(self, port: str) -> Optional[WaferInfo]:
         """Try to detect a wafer on the given port.