ui: labeled conclusion sections — 'Model solution' hero, 'Verdict' below

Owner round 2 (2026-10-05), Slice G: 'Solved' alone over unlabeled prose
didn't read as the model solution. The hero now carries its own 'Model
solution' section label (the quiz cards' register), and the verdict
section mirrors it — label muted, text at the same 50% register as quiz
explanations.

components/practice-cards.tsx

@@ -81,14 +81,21 @@ export function ConcludeCard({ part }: ArtifactPartProps) {
 			<div className="mb-1 text-xs font-medium uppercase tracking-wide text-muted-foreground">
 				{OUTCOME_LABEL[outcome] ?? "Concluded"}
 			</div>
+			{/* LABELED SECTIONS (owner round 2, 2026-10-05): 'Solved' alone over
+			    unlabeled prose didn't read as the model solution — the hero now
+			    carries its own label, and the verdict section mirrors it. Same
+			    register as the quiz cards' section labels. */}
 			{reveal.length > 0 && (
+				<div>
+					<div className="mb-0.5 text-xs font-medium uppercase tracking-wide text-muted-foreground">Model solution</div>
 					<div className="lh-prose text-[15px]">
 						<MessageResponse>{reveal}</MessageResponse>
 					</div>
+				</div>
 			)}
 			{verdict.length > 0 && (
-				<div className="mt-3 rounded-lg bg-muted py-2 text-sm text-muted-foreground">
+				<div className="mt-3 rounded-lg bg-muted py-2 text-sm text-foreground/50">
-					<span className="font-medium text-foreground">Verdict: </span>
+					<span className="font-medium text-muted-foreground">Verdict: </span>
 					<MessageResponse className="inline [&_p]:inline [&_p]:m-0">{verdict}</MessageResponse>
 				</div>
 			)}

tests/render-practice-surface.test.tsx

@@ -114,6 +114,7 @@ describe("the practice transcript cards", () => {
 		assert.match(html, /data-testid="conclude-card"/);
 		assert.match(html, /Solved with hints/);
 		assert.match(html, /Pair them; each pair is even\./, "the committed solution, verbatim");
+		assert.match(html, /Model solution/); // the labeled hero (owner round 2)
 		assert.match(html, /Verdict:/);
 		assert.match(html, /The pairing came after R2\./);
 		// The verdict row renders AFTER the solution (the hero first).