Move the CYW43439 (Pico W) WiFi emulation out of the open-source tree so it
can ship as a paid feature in a private overlay. OSS keeps a plain Pico W
(no WiFi); the overlay registers the cyw43 protocol + backend network stack
at runtime via generic seams.
Frontend:
- Add simulation/PioPeripheral.ts: a generic "PIO bus peripheral" seam
(feedWord / inDiscardableWriteData / resetFraming / hostWakeLevel /
onHostWake / onSimulationStart). No factory is installed in OSS, so
createPioPeripheral() returns null and a Pico W simulates as a plain Pico.
- RP2040Simulator: keep the fragile PIO-FIFO plumbing (it must re-run after
loadMicroPython swaps the chip) but drive it through PioPeripheral instead
of an inlined cyw43 import (attachCyw43 -> attachPioPeripheral, etc.).
- useSimulatorStore: generic attach/detach + setBoardWifiStatus; drop the
cyw43 bridge map.
- MicroPythonLoader: add registerFirmwareVariant() so an overlay can add the
RPI_PICO_W build; remove the OSS pico-w config + bundled .uf2.
- Delete simulation/cyw43/ (moved to the overlay).
Backend:
- core/hooks.py: add generic register_ws_sim_handler / dispatch_ws_sim_message
and register_gateway_proxy / dispatch_gateway_proxy seams.
- simulation.py: route start_picow / stop_picow / picow_packet_out through the
ws_sim_handler hook (the overlay handles + gates them).
- iot_gateway.py: resolve the Pico W gateway through the gateway_proxy hook.
- Delete services/picow_net/ + picow_net_bridge.py (moved to the overlay).
Tests: move the cyw43/picow suites to the overlay; update RP2040Simulator
mock stubs to attachPioPeripheral.