Plugin-based workflow for MicroPython firmware parsing, downloading, flashing, or manual confirmation. Used when Codex receives a phase_complete(select-hw) with next_phase=upy-flash-mpy-firmware-plugin; consumes the select-hw manifest_content, parses firmware from micropython.org/download or a trusted vendor source, assists with ESP32 esptool flashing, guides Pico/RP2 UF2 copying, or provides manual flash links for other boards, and finally outputs next_phase=upy-scaffold-plugin.
