P0-06: Delete the three stopgap Pico firmwares (Club_Pico, HouseSwarming_Pico, Fungi_Pico) #184

Part of #175 (audit Phase 0). Evidence: docs/audit/2026-11-09/detail/firmware-prototypes-pipes.md §1a.

Why. Firmware/Club_Pico/main.py, Firmware/HouseSwarming_Pico/main.py, Firmware/Fungi_Pico/main.py each open with "standalone Pico light controller (stopgap)". One-day commits on 2026-05-29/30. Zero references anywhere in ShowControl/, docs/, scripts/, or any ADR. Each copy-pastes the 15-line PIO SK6812 driver from TreeHouse_PicoLEDs. Each role is now covered by an ESP32-S3 target in Firmware/TreeHouse_Controllers/src/targets/ (swannatopia, jess, julia, dormer). Decision D1 confirmed the ESP32 boards are installed.

Do.

git rm -r Firmware/Club_Pico Firmware/HouseSwarming_Pico Firmware/Fungi_Pico

283 LOC, 3 files.

Done when. Directories gone. (Phase 1 item P1-05 adds a Firmware/README.md that lists them as retired.)