Wave-5 reskin batch 1: the token layer — palette, type ladder, radii ladder, fonts

- Palette per the owner's hexes: background #141414, raised #1C1C1C,
  edges #434343, ink tokens, destructs unchanged; :root and .dark carry
  identical values (the app is always dark).
- Type ladder declared once (11px base, each size carries its own
  line-height); radii ladder 4/8/12/16; spacing rhythm = Tailwind's 4px
  scale. All documented in the globals.css header.
- Fonts: JetBrains Mono (chrome) + Source Sans 3 (prose) via
  next/font/google in app/layout.tsx; CMU Serif bold bundled locally
  (public/fonts/cmunbx.ttf) behind the lh-cmu @font-face.
- Prose/emphasis tokens: --lh-ink-strong (rust bold), --lh-ink-italic
  (blue italic), .lh-prose wrapper — ready for the future settings UI.
- l.h-ink-strong/italic defaults sampled from the reference mockup.

app/layout.tsx

@@ -1,9 +1,15 @@
 import type { Metadata } from "next";
+import { JetBrains_Mono, Source_Sans_3 } from "next/font/google";
 import "katex/dist/katex.min.css";
 import "./globals.css";
 import { AppShell, SidebarProvider } from "@/components/sidebar";
 import { ActivityDock, ActivityProvider } from "@/components/activity-dock";
 
+// Chrome = JetBrains Mono, teaching prose = Source Sans 3, titles = CMU
+// Serif (the bundled lh-cmu @font-face in globals.css — no CDN).
+const ui = JetBrains_Mono({ subsets: ["latin"], variable: "--font-jetbrains" });
+const prose = Source_Sans_3({ subsets: ["latin"], variable: "--font-sans3" });
+
 export const metadata: Metadata = {
 	title: "Learning Harness",
 	description: "A teacher agent with a memory — sessions, quizzes, and a knowledge graph of what you know.",
@@ -12,7 +18,7 @@ export const metadata: Metadata = {
 export default function RootLayout({ children }: { children: React.ReactNode }) {
 	return (
 		<html lang="en" className="dark">
-			<body className="min-h-dvh antialiased">
+			<body className={`${ui.variable} ${prose.variable} min-h-dvh antialiased`}>
 			<SidebarProvider>
 									<ActivityProvider>
 						<AppShell>{children}</AppShell>