feat: dual BLE+USB serial — single firmware replaces separate BLE/USB builds

- DualSerialInterface: enable()/disable() control BLE only, USB always on;
  USB state machine not read while BLE connected to avoid partial-frame
  corruption; reset USB on BLE disconnect for clean reconnect
- Fix -UBLE_DEBUG_LOGGING (no space) to avoid PlatformIO SCons parse error
- build.sh: drop separate USB/BLE builds, dual_settings only
- wio-tracker-l1-eink: enable DUAL_SERIAL in companion_radio_ble build

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

variants/wio-tracker-l1-eink/platformio.ini

@@ -57,6 +57,7 @@ build_flags = ${WioTrackerL1Eink.build_flags}
   ; -D MESH_DEBUG=1
   -D UI_RECENT_LIST_SIZE=6
   -D UI_SENSORS_PAGE=1
+  -D DUAL_SERIAL
 build_src_filter = ${WioTrackerL1Eink.build_src_filter}
   +<helpers/nrf52/SerialBLEInterface.cpp>
   +<helpers/ui/MomentaryButton.cpp>

variants/wio-tracker-l1/platformio.ini

@@ -140,7 +140,7 @@ extra_scripts = post:create-uf2.py
 extends = WioTrackerL1CompanionBLE
 build_flags = ${WioTrackerL1CompanionBLE.build_flags}
   -D DUAL_SERIAL=1
-  -U BLE_DEBUG_LOGGING
+  -UBLE_DEBUG_LOGGING
 
 [env:WioTrackerL1_companion_radio_dual]
 extends = WioTrackerL1CompanionDual