feat(wio-tracker-l2): board layer + ui-new bring-up env

Seeed Wio Tracker L2 (ESP32-S3R8 16MB/8MB PSRAM, SX1262, NV3031B 320x240
QSPI LCD + GT911 touch + LP5814 backlight, TCA9535 expander gating every
rail, ADS1115 battery ADC, AW35615 USB-C, L76K GNSS).

Board layer ported from meshcore-dev/MeshCore PR #3381 (Hacuchino-hash),
kept at the same paths for an easy upstream merge. Differences:
- display: dropped the UIColor theme (not adopted in this fork)
- GpsTap diagnostics wrapper omitted; GNSS reads Serial1 directly
- nv3031b ODR fix dropped: LovyanGFX >= 1.2.30 (now pinned) defines
  Panel_NV3031B::init_cmds itself -- the fix became a duplicate symbol
- MESH_DEBUG_PRINTLN with a non-literal format fixed (broke MESH_DEBUG builds)
- upload_speed 115200: baud is virtual on native USB; skips the switch

solo/wio-tracker-l2 adds Wio_Tracker_L2_companion_solo_bringup: ui-new
zoomed 2x, BOOT button only, no touch -- a hardware smoke test, not a
release target (deliberately not *_solo_dual, so CI doesn't publish it).
The real UI for this board will be a new LVGL frontend.

Verified on hardware: boot, display, radio, GPS, battery, BLE app link.
First boot takes tens of seconds while SPIFFS formats its 3.4 MB partition.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

variants/wio-tracker-l2/target.cpp

@@ -0,0 +1,34 @@
+#include <Arduino.h>
+#include "target.h"
+
+WioTrackerL2Board board;
+
+static SPIClass spi;
+RADIO_CLASS radio = new Module(P_LORA_NSS, P_LORA_DIO_1, P_LORA_RESET, P_LORA_BUSY, spi);
+
+WRAPPER_CLASS radio_driver(radio, board);
+
+ESP32RTCClock fallback_clock;
+AutoDiscoverRTCClock rtc_clock(fallback_clock);
+MicroNMEALocationProvider gps(Serial1, &rtc_clock);
+EnvironmentSensorManager sensors(gps);
+
+#ifdef DISPLAY_CLASS
+  DISPLAY_CLASS display;
+  MomentaryButton user_btn(PIN_USER_BTN, 1000, true, true);
+#endif
+
+bool radio_init() {
+  MESH_DEBUG_PRINTLN("radio_init: rtc + sx1262 init");
+  fallback_clock.begin();
+  rtc_clock.begin(Wire);  // Wire already running on 47/48 from board.begin()
+
+  bool ok = radio.std_init(&spi);
+  MESH_DEBUG_PRINTLN("radio_init: SX1262 %s", ok ? "OK" : "FAILED");
+  return ok;
+}
+
+mesh::LocalIdentity radio_new_identity() {
+  RadioNoiseListener rng(radio);
+  return mesh::LocalIdentity(&rng);  // create new random identity
+}