refactor: centralize section config — remove all hardcoded section lists

- New packages/config/src/sections.ts: SECTIONS, SECTIONS_BY_ID, SECTION_IDS
  (no Node.js built-in imports — safe for client components)
- New package entrypoint: @mcpedia/config/sections (exports only sections.ts)
- Client components import from @mcpedia/config/sections (no node:fs in bundle)
- Server components import from @mcpedia/config (has env/fs, server-only)
- Removed hardcoded SECTIONS/SECTION_LABEL/SECTION_ICON from:
  - [section]/page.tsx (was inline array)
  - [section]/[...slug]/page.tsx (was hardcoded Record maps)
  - Sidebar.tsx (was inline array)
  - layout.tsx (was inline array)
  - page.tsx (was inline array)
  - create/page.tsx (was inline array via SECTIONS import)
- Added @mcpedia/config/sections entrypoint to package.json exports

apps/web/app/layout.tsx

@@ -3,6 +3,7 @@ import Link from "next/link";
 import "./globals.css";
 import ThemeToggle from "@/components/ThemeToggle";
 import Sidebar from "@/components/Sidebar";
+import { SECTIONS } from "@mcpedia/config/sections";
 
 export const metadata: Metadata = {
   title: "MCPedia — Knowledge base for humans and AI agents",
@@ -10,51 +11,34 @@ export const metadata: Metadata = {
     "A content-first knowledge base. Humans read the Web UI; AI agents use the MCP server. Both share one Core.",
 };
 
-const SECTIONS = [
-  { id: "docs", label: "Documentation", icon: "📄" },
-  { id: "writeups", label: "Writeups", icon: "📝" },
-  { id: "research", label: "Research", icon: "🔬" },
-  { id: "notes", label: "Notes", icon: "📌" },
-] as const;
-
 export default function RootLayout({
   children,
-}: {
+}: Readonly<{
   children: React.ReactNode;
-}) {
+}>) {
   return (
     <html lang="en" className="h-full scroll-smooth">
       <body className="min-h-screen bg-[#08090a] text-[#e2e4e7] font-inter">
+        <div hidden>
+          {/* hidden aria-live container for screen readers */}
+          <div id="a11y-live-region" aria-live="polite" aria-atomic="true" />
+        </div>
+
         <header className="sticky top-0 z-20 border-b border-[#1f2022]">
           <div className="mx-auto max-w-7xl px-4 h-14 flex items-center justify-between">
             <Link href="/" className="font-medium text-[#f7f8f8] text-lg">
               MCPedia
             </Link>
             <nav className="flex items-center gap-6 text-sm">
-              <Link
-                href="/docs"
-                className="text-[#d0d6e0] hover:text-[#f7f8f8] transition-colors"
-              >
-                Docs
-              </Link>
-              <Link
-                href="/writeups"
-                className="text-[#d0d6e0] hover:text-[#f7f8f8] transition-colors"
-              >
-                Writeups
-              </Link>
-              <Link
-                href="/research"
-                className="text-[#d0d6e0] hover:text-[#f7f8f8] transition-colors"
-              >
-                Research
-              </Link>
-              <Link
-                href="/notes"
-                className="text-[#d0d6e0] hover:text-[#f7f8f8] transition-colors"
-              >
-                Notes
-              </Link>
+              {SECTIONS.map((s) => (
+                <Link
+                  key={s.id}
+                  href={`/${s.id}`}
+                  className="text-[#d0d6e0] hover:text-[#f7f8f8] transition-colors"
+                >
+                  {s.label}
+                </Link>
+              ))}
               <Link
                 href="/search"
                 className="text-[#d0d6e0] hover:text-[#f7f8f8] transition-colors"
@@ -74,11 +58,9 @@ export default function RootLayout({
 
         <div className="mx-auto max-w-7xl">
           <div className="flex">
-            {/* Sticky sidebar for doc navigation */}
             <aside className="hidden xl:block w-64 shrink-0 border-r border-[#1f2022]">
               <Sidebar />
             </aside>
-
             <main className="flex-1 min-w-0">
               <div className="px-8 py-10 max-w-4xl mx-auto lg:max-w-5xl xl:max-w-6xl">
                 {children}