feat: scaffold electron orchestrator foundation

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/renderer/components/AppShell.tsx

@@ -0,0 +1,15 @@
+import type { ReactNode } from 'react';
+
+interface AppShellProps {
+  sidebar: ReactNode;
+  content: ReactNode;
+}
+
+export function AppShell({ sidebar, content }: AppShellProps) {
+  return (
+    <div className="flex min-h-screen bg-slate-950 text-slate-100">
+      <aside className="w-[360px] shrink-0 border-r border-slate-800 bg-slate-900/90">{sidebar}</aside>
+      <main className="min-w-0 flex-1">{content}</main>
+    </div>
+  );
+}