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>

test/check-vectors.js

@@ -0,0 +1,21 @@
+/* Re-renders every golden case with sim/engine.js and compares with test/vectors.
+   Exit code 0 = engine unchanged. Use the same files to test the C port. */
+var fs=require('fs'), path=require('path');
+var E=require('../sim/engine.js'), R=require('./render.js');
+var dir=path.join(__dirname,'vectors'), fail=0, n=0;
+var prim=JSON.parse(fs.readFileSync(path.join(dir,'primitives.json'),'utf8'));
+prim.mix.forEach(function(v){ n++; if(R.hex(E.mix(parseInt(v.a,16)>>>0,v.b))!==v.out){ fail++; console.log('mix',v.a,v.b,'differs'); } });
+prim.rng.forEach(function(v){ n++; var r=new E.Rng(parseInt(v.seed,16)>>>0); for(var i=0;i<16;i++) if(R.hex(r.next())!==v.next[i]){ fail++; console.log('rng',v.seed,'step',i,'differs'); break; } });
+prim.genomes.forEach(function(v){ n++; if(JSON.stringify(E.genome(parseInt(v.seed,16)>>>0))!==JSON.stringify(v.genome)){ fail++; console.log('genome',v.seed,'differs'); } });
+fs.readdirSync(dir).filter(function(f){ return /^gen\d/.test(f); }).sort().forEach(function(f){
+  JSON.parse(fs.readFileSync(path.join(dir,f),'utf8')).cases.forEach(function(c){
+    n++;
+    var got=R.renderCase({seed:parseInt(c.seed,16)>>>0,salts:c.salts,gen:c.gen,energy:c.energy,drift:c.drift,fillBars:c.fillBars,scale:c.scale,root:c.root},c.bars.length);
+    if(got.checksum===c.checksum) return;
+    fail++;
+    for(var b=0;b<c.bars.length;b++){ var a=JSON.stringify(c.bars[b].events), g=JSON.stringify(got.bars[b].events);
+      if(a!==g){ console.log('FAIL',c.id,'first difference in bar',b); break; } }
+  });
+});
+console.log(fail? fail+' of '+n+' checks FAILED' : 'all '+n+' checks pass');
+process.exit(fail?1:0);