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/pots.c

@@ -0,0 +1,31 @@
+#include "pots.h"
+#include "hardware/adc.h"
+
+#define SAMPLES    16
+#define HYSTERESIS 24   /* in 12-bit counts: 0.75 of a 7-bit step past the step's centre */
+
+static int value[2], raw[2];
+
+void pots_init(void){
+  adc_init();
+  adc_gpio_init(26);   /* also turns off the digital input and pulls */
+  adc_gpio_init(27);
+  pots_update();
+  value[0] = raw[0] >> 5; value[1] = raw[1] >> 5;
+}
+
+void pots_update(void){
+  int i, k;
+  for(i = 0; i < 2; i++){
+    int sum = 0, centre, d;
+    adc_select_input((uint)i);
+    for(k = 0; k < SAMPLES; k++) sum += adc_read();
+    raw[i] = sum / SAMPLES;
+    centre = value[i] * 32 + 16;
+    d = raw[i] - centre;
+    if(d > 16 + HYSTERESIS || d < -16 - HYSTERESIS) value[i] = raw[i] >> 5;
+  }
+}
+
+int pot_value(int pot){ return value[pot]; }
+int pot_raw(int pot){ return raw[pot]; }