* Add Meshnology W12 (WiFi LoRa 32 V5) variant with LR2021 radio
ESP32-S3R8 + 16 MB flash + Semtech LR2021 dual-band LoRa + SSD1315 OLED,
Heltec V3-style pinout.
Pin map comes from the vendor pin sheet and vendor Arduino demos, confirmed
on hardware: I2C scan finds the OLED at 0x3C on SDA17/SCL18, and the LR2021
answers on NSS=8 SCK=9 MISO=11 MOSI=10 with BUSY=13/NRESET=12 verified by
reset-pulse probing.
The IRQ line needs LR2021_IRQ_DIO_NUM 8. RadioLib defaults irqDioNum to 5,
but DIO5 is not bonded out on this board - the two IRQ lines are DIO7 -> IO7
and DIO8 -> IO14, established by driving each radio DIO as a GPIO output and
watching which ESP32 pin followed. Left at the default, every interrupt is
routed to a floating pin: RX/TX still appear to work because
RadioLibInterface::pollMissedIrqs() falls back to polling the IRQ status
register, but the blocking scanChannel() waits on the pin itself and never
returns.
A shadow pins_arduino.h is needed because the generic esp32s3 one defines
RGB_BUILTIN, which pulls the Arduino RMT HAL into the link and fails against
this build's FreeRTOS config.
* Address review: add W12 variant metadata, trim comments
Declares the custom_meshtastic_* metadata the build manifest expects. Without
it the emitted .mt.json carried no hwModel, slug, display name or support
level, so the board was invisible to the flasher - and board_level = extra
kept it out of PR builds entirely, which is why it never appeared in this
PR's board list. It now matches the W10 sibling at board_level = pr with
support level 1. hwModel stays 255/PRIVATE_HW until a W12 enum lands in the
protobufs.
Also trims the header comments to the one-or-two-line limit in AGENTS.md;
the vendor pin sheet and probing evidence live in the PR description.