kb: bootstrap foundation + jazz guitar gold standard

SCHEMA.md authoring contract, validate-kb.mjs quality gate (pitch-class
verification of shapes against chord qualities), registry, and the jazz
style: 5 progressions x 2 guitar plays (shells + drop-2), comping
rhythms, improv guidance, sourced licks. Validator and vite build green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/data/kb/index.js

@@ -0,0 +1,13 @@
+// KB registry — the UI reads only this. Each style folder registers here;
+// instruments appear as their cells are completed (see docs/kb-backlog.md).
+import jazzMeta from './jazz/meta.js'
+import jazzProgressions from './jazz/progressions.js'
+import jazzGuitar from './jazz/guitar.js'
+
+export default {
+  jazz: {
+    meta: jazzMeta,
+    progressions: jazzProgressions,
+    instruments: { guitar: jazzGuitar },
+  },
+}