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>

package.json

@@ -0,0 +1,12 @@
+{
+  "name": "seedbox",
+  "version": "0.1.0",
+  "private": true,
+  "description": "Generative rhythm and melody machine for the Raspberry Pi Pico 2 W (browser simulator, golden vectors, hardware docs)",
+  "scripts": {
+    "test": "node test/check-vectors.js && node hardware/check-layout.js",
+    "vectors": "node test/gen-vectors.js",
+    "layout": "node hardware/check-layout.js --nets",
+    "wiring": "node hardware/check-layout.js && node tools/build-wiring.js"
+  }
+}