feat: add Russian localization and independent STT languages

app/api/chats/[id]/markdown/route.ts

@@ -11,14 +11,14 @@
  * markers are invisible by the engine's law).
  */
 import { sessionMarkdown } from "@/src/core";
-import { getChat } from "@/src/server";
+import { getChat, applicationLanguage } from "@/src/server";
 
 /** Filename-safe title (own module scope on purpose: tiny + pure). */
 function slugify(title: string): string {
 	const slug = title
 		.toLowerCase()
 		.normalize("NFKD")
-		.replace(/[^a-z0-9]+/g, "-")
+		.replace(/[^\p{L}\p{N}]+/gu, "-")
 		.replace(/^-+|-+$/g, "");
 	return slug.length > 0 ? slug : "session";
 }
@@ -27,11 +27,11 @@ export async function GET(_req: Request, ctx: { params: Promise<{ id: string }>
 	const { id } = await ctx.params;
 	const record = getChat(id);
 	if (!record) return Response.json({ error: "Unknown chat" }, { status: 404 });
-	const markdown = sessionMarkdown(record.messages, { title: record.title, anchors: false });
+	const markdown = sessionMarkdown(record.messages, { title: record.title, anchors: false, language: applicationLanguage(_req.headers.get("accept-language")) });
 	return new Response(markdown, {
 		headers: {
 			"content-type": "text/markdown; charset=utf-8",
-			"content-disposition": `attachment; filename="${slugify(record.title)}.md"`,
+			"content-disposition": `attachment; filename="${/^[a-z0-9-]+$/.test(slugify(record.title)) ? slugify(record.title) : "session"}.md"; filename*=UTF-8''${encodeURIComponent(slugify(record.title))}.md`,
 		},
 	});
 }

app/api/graph/import/route.ts

@@ -13,7 +13,7 @@
  * healthy. The dock's chips + graph refetch track progress live through
  * /api/graph/status, as with session runs.
  */
-import { extraction, NotesImportError } from "@/src/server";
+import { extraction, NotesImportError, applicationLanguage } from "@/src/server";
 import {
 	ModelsNotConfiguredError,
 	PROVIDER_KEY_MISSING_CODE,
@@ -56,7 +56,7 @@ export async function POST(request: Request) {
 			const { file, requestIndex } = next;
 			try {
 				const text = await file.text();
-				const stats = await extraction.importNotes({ filePath: file.name, text });
+				const stats = await extraction.importNotes({ filePath: file.name, text, language: applicationLanguage(request.headers.get("accept-language")) });
 				results.push({ filePath: file.name, requestIndex, outcome: "completed", ok: true, stats });
 			} catch (err) {
 				if (err instanceof ModelsNotConfiguredError) {

app/globals.css

@@ -598,3 +598,6 @@ body {
 	outline: 1px solid var(--border);
 	border-radius: 0.25rem;
 }
+
+/* Source Sans 3 lacks Cyrillic; Russian prose uses the bundled Noto Sans subset. */
+html[lang="ru"] { --font-sans3: var(--font-russian-prose); }

app/layout.tsx

@@ -1,5 +1,9 @@
+import { headers } from "next/headers";
+import { readSettingsRecord } from "@/src/server";
+import { resolveLanguage, systemLanguage, translate } from "@/src/core";
+import { I18nProvider } from "@/components/i18n";
 import type { Metadata } from "next";
-import { JetBrains_Mono, Source_Sans_3 } from "next/font/google";
+import { JetBrains_Mono, Source_Sans_3, Noto_Sans } from "next/font/google";
 import "katex/dist/katex.min.css";
 import "./globals.css";
 import { AppShell, SidebarProvider } from "@/components/sidebar";
@@ -10,21 +14,29 @@ import UpdateBanner from "@/components/update-banner";
 
 // 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 ui = JetBrains_Mono({ subsets: ["latin", "cyrillic"], 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.",
-};
+const russianProse = Noto_Sans({ subsets: ["latin", "cyrillic"], variable: "--font-russian-prose" });
 
-export default function RootLayout({ children }: { children: React.ReactNode }) {
+export async function generateMetadata(): Promise<Metadata> {
+	const language = resolveLanguage(readSettingsRecord()?.general?.language, (await headers()).get("accept-language"));
+	return {
+	title: "Learning Harness",
+	description: translate(language, "A teacher agent with a memory — sessions, quizzes, and a knowledge graph of what you know."),
+	};
+}
+
+export default async function RootLayout({ children }: { children: React.ReactNode }) {
+	const general = readSettingsRecord()?.general ?? {};
+	const system = systemLanguage((await headers()).get("accept-language"));
+	const language = resolveLanguage(general.language, system);
 	return (
-		<html lang="en" className={`dark ${ui.variable} ${prose.variable}`}>
+		<html lang={language} className={`dark ${ui.variable} ${prose.variable} ${russianProse.variable}`}>
 			<body className="min-h-dvh antialiased">
 			{/* The notification channel rides OUTSIDE everything: sidebar, dock,
 				 and pages all subscribe as the polls retire (push S3, 2026-10-02). */}
-			<ServerEventsProvider>
+			<I18nProvider initialGeneral={general} system={system}><ServerEventsProvider>
 				<AppearanceProvider>
 					<SidebarProvider>
 						<ActivityProvider>
@@ -35,6 +47,7 @@ export default function RootLayout({ children }: { children: React.ReactNode })
 			</ServerEventsProvider>
 			{/* Auto-update banner (Wave C): fixed card, Electron-only pushes. */}
 			<UpdateBanner />
+		</I18nProvider>
 		</body>
 		</html>
 	);