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>

README.md

@@ -0,0 +1,59 @@
+# Seedbox
+
+A generative rhythm and melody machine for a Raspberry Pi Pico 2 W. One 32-bit seed grows a whole tune: a drum part for any sampler or drum machine and a bass, melody and pad line for a poly synth, both over MIDI. Built and tested with a Roland SP-404MKII and an Arturia MiniFreak. You don't program steps. You pick a seed, turn tracks on and off, and steer it with two knobs.
+
+**Status: v0.1.** The engine and the controls are settled in a browser simulator that drives the real gear over Web MIDI. The stripboard layout has been checked by script and by an independent review. The Pico firmware is not written yet: that's the next step.
+
+## What's in the box
+
+| Part | |
+|---|---|
+| Brain | Raspberry Pi Pico 2 W (RP2350), powered and flashed through its own USB port at the back |
+| Screen | Nokia 5110 LCD (PCD8544, 84 × 48) |
+| Controls | Encoder with push, ENERGY and DRIFT pots, SEED button, 11 track buttons in a 4 × 3 grid, with the RUN toggle in its top-right corner |
+| MIDI | IN (for learning drum pads), OUT KIT (sampler or drum machine), OUT SYNTH. 3.5 mm TRS (Type A), MIDI 1.0 3.3 V spec. |
+
+## Repo map
+
+```
+sim/            the browser simulator: index.html, engine.js (portable engine), app.js (UI, Web MIDI)
+test/           golden vectors and the scripts that make and check them
+hardware/       layout.js (the stripboard, one source of truth) and check-layout.js
+tools/          bench pages: wiring.html, bom.html (tick-off parts list), panel.html (panel layout)
+docs/           concept, controls, MIDI setup, hardware (BOM, pinout, wiring, panel, SVG drawings)
+firmware/       the port plan for the Pico (C, Pico SDK)
+```
+
+## Run it
+
+The simulator is a static page. Web MIDI needs a secure context, so serve it over `localhost` or HTTPS rather than opening the file directly:
+
+```sh
+npx serve .            # or: python3 -m http.server
+# open http://localhost:3000/sim/   (Chrome or Edge; Firefox needs a Web MIDI add-on)
+```
+
+GitHub Pages works too: enable Pages for the repo and open `/sim/`.
+
+Checks (Node 18 or later, no dependencies):
+
+```sh
+npm test               # golden vectors + stripboard netlist
+```
+
+## Docs
+
+- [Concept](docs/concept.md): how the music is made
+- [Controls](docs/controls.md): the panel, the screen pages, the gestures
+- [MIDI setup](docs/midi-setup.md): kit and synth, learn mode
+- [Hardware](docs/hardware/README.md): parts, pinout, stripboard, panel
+- [Firmware plan](firmware/README.md)
+- [Design decisions](docs/decisions.md)
+
+## Licence
+
+None chosen yet. Add a `LICENSE` file before making the repo public (MIT for code and CC BY-SA for the hardware docs is a common pairing).
+
+## Credits
+
+The track model leans on Eric Lyon's paper "Techno Counterpoint", an analysis of Aphex Twin's tracking practice. The AMENIZER plays a re-voiced Amen break pattern (The Winstons, "Amen, Brother", 1969).