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).

tests/render-settings.test.tsx

@@ -155,7 +155,7 @@ describe("AgentSection (thin SSR)", () => {
 		);
 		// The trigger shows the stored id even with no catalog loaded (a
 		// trigger reading "Default" over a live override would lie).
-		assert.ok(html.includes("Glm 4.7 Flash"), "the override id is visible (prettyModel form)");
+		assert.ok(html.includes("glm 4.7 flash"), "the override id is visible (prettyModel form, no auto-caps)");
 		assert.ok(tagOf(html, "toggle-tool-demo").includes('aria-checked="false"'), "demo off");
 		assert.ok(tagOf(html, "toggle-tool-visual").includes('aria-checked="true"'), "visual still on");
 	});