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.

tests/test_stream_reader.py

@@ -3,11 +3,30 @@ from pygui.backend.models.frame import Frame
 from pygui.serialcomm.stream_reader import StreamReader
 
 class FakeTransport:
-    """Yield canned line then blocks (returns b'')."""
-    def __init__(self, lines): self._lines = list(lines); self.closed = False
+    """Yield canned data then blocks (returns b'')."""
+    def __init__(self, lines):
+        self._data = b"".join(lines)
+        self._pos = 0
+        self.closed = False
+    def read(self, n=1):
+        time.sleep(0.001)
+        if self._pos >= len(self._data):
+            return b""
+        res = self._data[self._pos:self._pos+n]
+        self._pos += n
+        return res
     def readline(self):
         time.sleep(0.001)
-        return self._lines.pop(0) if self._lines else b""
+        if self._pos >= len(self._data):
+            return b""
+        idx = self._data.find(b"\n", self._pos)
+        if idx == -1:
+            res = self._data[self._pos:]
+            self._pos = len(self._data)
+            return res
+        res = self._data[self._pos:idx+1]
+        self._pos = idx + 1
+        return res
     def close(self): self.closed = True
     
 def parse_line(raw: str, seq: int) -> Frame: