Set up nRF Connect SDK development environment #6

Install nRF Connect SDK v3.2.1, create a custom supermini_nrf52840 board definition (HWMv2 format), and verify with a hello_world build.

Steps

1. Install prerequisites (dtc, Python venv, west)
2. Init SDK workspace at ~/ncs via west init --mr v3.2.1
3. west update + west zephyr-export + west sdk install
4. Create supermini_nrf52840 board definition in boards/supermini/ (13 files)
5. Create minimal blink + USB serial firmware in firmware/
6. Document setup in docs/setup.md
7. west build -b supermini_nrf52840/nrf52840/uf2 firmware/

Done when

• west build -b supermini_nrf52840/nrf52840/uf2 succeeds and produces a .uf2
• docs/setup.md documents full dev environment setup
• hello_world blink running on SuperMini (manual flash via UF2)
• USB serial output works