Tier 2: WiFi + Bluetooth ELM327 transports

- obdcore/transport.py: pluggable byte transports -- SerialTransport,
  TcpTransport (WiFi ELM327, stdlib socket), BleTransport (experimental, via
  optional 'bleak'; background asyncio loop buffering notifications). ble_scan().
- ElmLink refactored onto a transport with .serial()/.tcp()/.ble() factories
  (close/cmd now go through self.io); no behavior change for serial.
- Controller.connect(conn={kind:serial|wifi|ble,...}); GUI connection bar gains
  a transport selector (Serial/USB/BT-SPP | WiFi host:port | Bluetooth LE + Scan).
- Classic-Bluetooth needs no new code (pairs as a serial port); WiFi needs no
  extra deps; BLE is opt-in (bleak not bundled, so CI binaries keep building).
- tests/test_transport.py: drives ElmLink over a fake ELM TCP server end-to-end
  (connect, RPM, readiness, VIN). All suites pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016yT89n4zR4qbrySoSiEyZs

obdcore/link.py

@@ -74,25 +74,40 @@ def find_ports():
 class ElmLink:
     PROMPT = b">"
 
-    def __init__(self, port, baud=38400, verbose=False):
-        if serial is None:
-            raise RuntimeError("pyserial not installed (pip install pyserial)")
+    def __init__(self, transport, verbose=False):
+        """transport: any object with write/read/reset_input_buffer/close.
+        Use the .serial() / .tcp() / .ble() factory helpers to build one."""
+        self.io = transport
         self.verbose = verbose
-        self.ser = serial.Serial(port, baud, timeout=0.2)
         self.protocol = "?"
         time.sleep(0.3)
-        self.ser.reset_input_buffer()
+        self.io.reset_input_buffer()
+
+    @classmethod
+    def serial(cls, port, baud=38400, **kw):
+        from . import transport as tp
+        return cls(tp.SerialTransport(port, baud), **kw)
+
+    @classmethod
+    def tcp(cls, host, port=35000, **kw):
+        from . import transport as tp
+        return cls(tp.TcpTransport(host, port), **kw)
+
+    @classmethod
+    def ble(cls, address, **kw):
+        from . import transport as tp
+        return cls(tp.BleTransport(address), **kw)
 
     # -- low-level --
     def cmd(self, s, settle=0.0, timeout=4.0):
-        self.ser.reset_input_buffer()
-        self.ser.write((s + "\r").encode())
+        self.io.reset_input_buffer()
+        self.io.write((s + "\r").encode())
         if settle:
             time.sleep(settle)
         buf = bytearray()
         deadline = time.time() + timeout
         while time.time() < deadline:
-            chunk = self.ser.read(256)
+            chunk = self.io.read(256)
             if chunk:
                 buf += chunk
                 if self.PROMPT in buf:
@@ -209,6 +224,6 @@ class ElmLink:
 
     def close(self):
         try:
-            self.ser.close()
+            self.io.close()
         except Exception:
             pass