feat(kb): gospel piano cell — 14 plays across all 7 progressions (task P-23)

Church pillars vs rootless, hymn 12/8 vs octave-6/9, passing-dim walks
vs praise clusters, worship pads vs anticipated stabs; gospel comping
cells distinct from jazz's. KB: 140 plays. Critic returned once (one
improv-row scale claim false for vi7/iii7 — split into arithmetic-exact
rows), PASS on re-gate; 39/40 first-pass claims held.

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

src/data/kb/index.js

@@ -28,6 +28,7 @@ import rnbGuitar from './rnb/guitar.js'
 import gospelMeta from './gospel/meta.js'
 import gospelProgressions from './gospel/progressions.js'
 import gospelGuitar from './gospel/guitar.js'
+import gospelPiano from './gospel/piano.js'
 import popMeta from './pop/meta.js'
 import popProgressions from './pop/progressions.js'
 import popGuitar from './pop/guitar.js'
@@ -76,7 +77,7 @@ export default {
   gospel: {
     meta: gospelMeta,
     progressions: gospelProgressions,
-    instruments: { guitar: gospelGuitar },
+    instruments: { guitar: gospelGuitar, piano: gospelPiano },
   },
   pop: {
     meta: popMeta,