ui: the chat comeback — side-based authorship, restored quotes, tucked whys

Blockquotes: the callout override had displaced Streamdown's own styled
blockquote component, so plain quotes rendered as bare unstyled text
since that commit. The pass-through branch now restores Streamdown's
verbatim classes (border-l-4, muted italic).

Explanations tucked for ALL questions (owner): the prediction's Why /
Hide-why toggle is universal — every quiz answered card sits its
explanation behind the same collapsed button. Same pattern, one law.

The thinking row's rhythm: my-1 -> my-3. The 4px margin hugged the
options on non-graded answered cards (owner report); 12px matches the
card's mt-2/mt-3 spacing grammar everywhere the row renders.

Side-based authorship (owner round, 2026-10-07): the document shape
blurred user into agent — three left-rail idioms (user text, user
thinking, quoted prose) collided once quotes rendered. User rows go
RIGHT: 'You' messages and practice thinking cards hug the right edge at
85% width with the rail mirrored (border-r), text still reading
left-to-right. In-card thinking (inside the answered card, the agent's
context) stays left. Transcript thinking rows arrive EXPANDED — the
thinking was clearly sent. Cmd+T (toggle-user-thinking, chat scope,
cheat-sheet row) sets every user-thinking row to one state via a module
store: explicit sets stomp individual toggles, late mounts honor the
last set (the state initializer reads the store, so static render
reflects it too).

components/practice-cards.tsx

@@ -291,7 +291,10 @@ function MetadataPopover({
 
 export function ThinkingCard({ data }: { data: PracticeThinkingData }) {
 	// The unified row (owner rounds, 2026-10-05): one style, one label —
-	// collapsed arrival, "Your thinking", 50%-italic quote block on expand.
-	// Legacy records' commit flag is deliberately unread (one lane now).
-	return <ThinkingBlock testId="thinking-card" label="YOUR THINKING" text={data.text} />;
+	// 50%-italic quote block on expand. Legacy records' commit flag is
+	// deliberately unread (one lane now). A TRANSCRIPT row (owner round,
+	// 2026-10-07): mirrored to the right side, arriving expanded.
+	return (
+		<ThinkingBlock testId="thinking-card" label="YOUR THINKING" text={data.text} mirror defaultOpen />
+	);
 }