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).

src/core/keyboard.ts

@@ -40,7 +40,8 @@ export type KeyAction =
 	| "question-prev-row"
 	| "question-pick-row"
 	| "question-submit"
-	| "open-settings";
+	| "open-settings"
+	| "toggle-user-thinking";
 
 /** Where the cheat sheet groups an action (display only — dispatch is
  *  global; a seam that isn't mounted simply no-ops). */
@@ -71,6 +72,7 @@ export const KEYBOARD_ACTIONS: readonly KeyActionDef[] = [
 	{ id: "jump-graph", label: "Graph view", scope: "global", binding: "mod+g" },
 	{ id: "new-session", label: "New session", scope: "global", binding: "mod+n" },
 	{ id: "rename-session", label: "Rename session", scope: "chat", binding: "f2" },
+	{ id: "toggle-user-thinking", label: "Toggle all your thinking", scope: "chat", binding: "mod+t" },
 	// ⌘F is surface-scoped (owner key map): the graph focuses node search; a
 	// chat-scoped transcript search rides the same event when it lands (the
 	// graph's listener simply isn't mounted on chat pages).