ui: consistency sweep — the 1ch rail geometry, Submit thinking, no auto-caps

Owner round 4 (2026-10-05):

- THE RAIL IS THE MISSING CHARACTER: rail + padding = exactly 1ch of
  the mono heading font. 'YOUR THINKING' (13ch) + rail == 'AGENT
  THINKING' (14ch) flush — the chevrons line up vertically, no fixed
  columns. The YOU heading joins the rail (label inside, like the
  thinking rows) — one quote geometry everywhere.
- HEADING REGISTER: YOUR THINKING / AGENT THINKING / YOU all use the
  card eyebrows' small mono caps (text-xs = the 11px rung, font-medium
  uppercase tracking-wide) — the app chrome is JetBrains Mono.
- SUBMIT THINKING: the practice button is now literally the question
  dock's Button (h-9, px-3.5) in one p-1 row with the hint left
  ('↵ submits · ⇧↵ newline') — the keyboard hints are back. Corner
  radii concentric in both docks: shell 16 − 6 = field 10 − 4 = button 6
  (rounded-[10px] fields, rounded-[6px] buttons — the old rounded-xl/12
  was the 'too large' culprit).
- MODEL NAMES: prettyModel no longer auto-capitalizes — names render
  exactly as their providers write them ('glm 5.3 flash').
- Quiz explanations pulled closer (mt-3 → mt-2).

components/question-dock.tsx

@@ -769,7 +769,7 @@ function QuestionDockForm({
 			>
 				<div
 					data-testid={qd.mode === "text" ? "answer-field" : "thinking-field"}
-					className="rounded-xl border border-border/70 bg-background/60 transition-colors focus-within:border-primary/50"
+					className="rounded-[10px] border border-border/70 bg-background/60 transition-colors focus-within:border-primary/50"
 				>
 					<div className="px-2.5 pt-2 text-xs font-medium uppercase tracking-wide text-muted-foreground">
 						{qd.mode === "text" ? "Your answer" : "YOUR THINKING"}
@@ -846,7 +846,7 @@ function QuestionDockForm({
 						<Button
 							type="submit"
 							disabled={!canSubmit}
-							className="ml-auto h-9 rounded-[10px] px-3.5 text-sm font-medium"
+							className="ml-auto h-9 rounded-[6px] px-3.5 text-sm font-medium"
 						>
 							Submit answer
 						</Button>