feat(trythis): side-by-side suggestions with per-chord instrument diagrams (task L-75)

Try this now shows all of the current chord's valid substitutions at
once (no more rotation), each as a card with the chord name, a mini
diagram of how to play it in the selected instrument (guitar
ChordDiagram 4-across, piano MiniPiano keyboards in a 2x2, bass a root
caption), and the plain why. Still follows the live playhead so the
set refreshes per chord as the progression evolves; honest-empty
without a key/loop; the rolled-jam visibility fallback preserved.
App.jsx change is the single instrument prop, contract-clean. Critic
PASS (combined gate: diagrams resolve, root badge correct, reactivity
verified).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/App.jsx

@@ -861,6 +861,7 @@ export default function App() {
               keyInfo={effectiveKey}
               currentChord={currentChord}
               onChordClick={setSelectedChord}
+              instrument={instrument}
             />
             <RelatedProgressions
               loop={detectedProgression}