Seedbox v0.1 + firmware, generic kit/synth, ROOT/SCALE pages

First commit of the repo. Contents beyond the v0.1 simulator and layout:

- Full Pico 2 W firmware (firmware/app, drivers, engine port, host test).
- BANK page and 404 mode A/B removed; learned pads play exactly what was learned.
- 404/MiniFreak renamed to KIT/SYNTH throughout (jacks, code, sim, docs,
  layout labels; wiring rebuilt).
- ROLL returns to page select after a re-roll; a freshly learned track turns on.
- LCD contrast 66.
- ROOT and SCALE pages: 21 scales, AUTO = the seed picks; global and sticky.

Intended music change: the scale table grew from 8 to 21 and AUTO picks from
all of them, so every seed's scale changed. Vectors regenerated with
npm run vectors, plus new key-override cases. Flash record is now version 2.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

firmware/CMakeLists.txt

@@ -0,0 +1,42 @@
+# Seedbox firmware for the Pico 2 W.
+#   cmake -S firmware -B firmware/build -G Ninja && ninja -C firmware/build
+# Needs PICO_SDK_PATH (SDK 2.1 or later). The host engine test is separate: firmware/test/Makefile.
+cmake_minimum_required(VERSION 3.13)
+
+set(PICO_BOARD pico2_w CACHE STRING "Board type")
+include(pico_sdk_import.cmake)
+project(seedbox C CXX ASM)
+set(CMAKE_C_STANDARD 11)
+pico_sdk_init()
+
+# the portable engine, the same source the host test checks
+add_library(seedbox_engine INTERFACE)
+target_sources(seedbox_engine INTERFACE ${CMAKE_CURRENT_LIST_DIR}/engine/engine.c)
+target_include_directories(seedbox_engine INTERFACE ${CMAKE_CURRENT_LIST_DIR}/engine)
+
+add_library(seedbox_drivers INTERFACE)
+target_sources(seedbox_drivers INTERFACE
+  ${CMAKE_CURRENT_LIST_DIR}/drivers/midi_uart.c
+  ${CMAKE_CURRENT_LIST_DIR}/drivers/pcd8544.c
+  ${CMAKE_CURRENT_LIST_DIR}/drivers/inputs.c
+  ${CMAKE_CURRENT_LIST_DIR}/drivers/encoder.c
+  ${CMAKE_CURRENT_LIST_DIR}/drivers/pots.c)
+target_include_directories(seedbox_drivers INTERFACE ${CMAKE_CURRENT_LIST_DIR}/drivers)
+target_link_libraries(seedbox_drivers INTERFACE pico_stdlib hardware_uart hardware_spi hardware_adc)
+
+# bring-up: board test over USB serial
+add_executable(seedbox_bringup bringup/main.c)
+target_compile_options(seedbox_bringup PRIVATE -Wall -Wextra)
+target_link_libraries(seedbox_bringup seedbox_engine seedbox_drivers pico_stdlib pico_cyw43_arch_none)
+pico_enable_stdio_usb(seedbox_bringup 1)    # also keeps the reset interface for picotool reboot -f -u
+pico_enable_stdio_uart(seedbox_bringup 0)   # UART0 is MIDI: stdio on it would send text to the kit device
+pico_add_extra_outputs(seedbox_bringup)
+
+# the instrument: core 0 UI, core 1 sequencer
+add_executable(seedbox app/main.c app/sequencer.c app/storage.c)
+target_compile_options(seedbox PRIVATE -Wall -Wextra)
+target_include_directories(seedbox PRIVATE app)
+target_link_libraries(seedbox seedbox_engine seedbox_drivers pico_stdlib pico_multicore pico_flash pico_rand hardware_flash)
+pico_enable_stdio_usb(seedbox 1)    # keeps the reset interface: picotool reboot -f -u flashes with the box closed
+pico_enable_stdio_uart(seedbox 0)   # UART0 is MIDI
+pico_add_extra_outputs(seedbox)