kb: add rock guitar pack; schema gains declared omit3 (power chords)

5 progressions (Mixolydian vamp, I-IV-V, minor descent, axis, Dorian
riff cell) x 2 plays: open-chord Malcolm hits, second-guitar triads,
Keith sus figure, power-chord chug, Police add9 arpeggios, thumb-over
embellishments. omit3 is a declared omission like rootless - the
pitch-class check still applies. Validator and build green.

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

src/data/kb/index.js

@@ -6,6 +6,9 @@ import jazzGuitar from './jazz/guitar.js'
 import bluesMeta from './blues/meta.js'
 import bluesProgressions from './blues/progressions.js'
 import bluesGuitar from './blues/guitar.js'
+import rockMeta from './rock/meta.js'
+import rockProgressions from './rock/progressions.js'
+import rockGuitar from './rock/guitar.js'
 
 export default {
   jazz: {
@@ -18,4 +21,9 @@ export default {
     progressions: bluesProgressions,
     instruments: { guitar: bluesGuitar },
   },
+  rock: {
+    meta: rockMeta,
+    progressions: rockProgressions,
+    instruments: { guitar: rockGuitar },
+  },
 }