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/drivers/encoder.h

@@ -0,0 +1,15 @@
+/* Quadrature encoder on GP10 (A) / GP11 (B), pull-ups, decoded in the GPIO interrupt with a state table.
+   The bench encoder gives 4 edges per click and rests with both contacts open (A = B = 1). As wired, the raw
+   count runs down when turned clockwise, so the driver flips it: + = clockwise.
+   A click counts when the shaft comes back to rest, so jitter around a detent doesn't count. */
+#ifndef SEEDBOX_ENCODER_H
+#define SEEDBOX_ENCODER_H
+
+#include <stdint.h>
+
+void    encoder_init(void);
+int32_t encoder_count(void);   /* clicks, + = clockwise */
+int32_t encoder_steps(void);   /* raw edges, for the bench */
+int     encoder_ab(void);      /* current A << 1 | B */
+
+#endif