- Replace ARM tarball download with gcc-arm-none-eabi from apt - Drop TARGETARCH/GCC_VERSION build args — no longer needed - Pin nrfx submodule to v2.9.0 which still bundles mdk/ headers - nrfx 3+ dropped mdk/ from the repo
- Fully open toolchain: arm-none-eabi-gcc inside Podman/Docker container - Platform-agnostic build via justfile (auto-detects podman vs docker) - CMake + Ninja build system with arm-none-eabi toolchain file - nRF52840 linker script and startup with full 64-entry vector table - Register access via typed bitfield unions (include/regs.h) - FHSS channel sequencer: AES-128-ECB PRNG over 40 channels (2402-2480 MHz) - Low-power sleep via SYSTEM_ON WFI + GPIOTE wakeup on button press - Vendor deps as shallow git submodules: nrfx, CMSIS_5, tiny-AES-c
