feat: React app shell with router, sidebar layout

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/App.tsx

@@ -1,9 +1,28 @@
-function App() {
+import { BrowserRouter, Routes, Route, Navigate } from "react-router-dom";
+import AppLayout from "./components/layout/AppLayout";
+
+function EmptyState() {
   return (
-    <div className="min-h-screen bg-gray-50 text-gray-900">
-      <h1 className="text-2xl font-bold p-8">Orchai</h1>
+    <div className="flex items-center justify-center h-full text-gray-400">
+      <p>Select a project or create a new one</p>
     </div>
   );
 }
 
+function App() {
+  return (
+    <BrowserRouter>
+      <Routes>
+        <Route element={<AppLayout />}>
+          <Route index element={<EmptyState />} />
+          <Route path="/projects/new" element={<div className="p-8">Create project (coming next)</div>} />
+          <Route path="/projects/:projectId" element={<div className="p-8">Project dashboard (coming next)</div>} />
+          <Route path="/projects/:projectId/edit" element={<div className="p-8">Edit project (coming next)</div>} />
+          <Route path="*" element={<Navigate to="/" replace />} />
+        </Route>
+      </Routes>
+    </BrowserRouter>
+  );
+}
+
 export default App;

src/components/layout/AppLayout.tsx

@@ -0,0 +1,13 @@
+import { Outlet } from "react-router-dom";
+import Sidebar from "./Sidebar";
+
+export default function AppLayout() {
+  return (
+    <div className="flex h-screen">
+      <Sidebar />
+      <main className="flex-1 overflow-y-auto bg-gray-50">
+        <Outlet />
+      </main>
+    </div>
+  );
+}

src/components/layout/Sidebar.tsx

@@ -0,0 +1,63 @@
+import { useEffect, useState } from "react";
+import { Link, useParams } from "react-router-dom";
+import { listProjects } from "../../lib/api";
+import type { Project } from "../../lib/types";
+
+export default function Sidebar() {
+  const [projects, setProjects] = useState<Project[]>([]);
+  const { projectId } = useParams();
+
+  useEffect(() => {
+    listProjects().then(setProjects);
+  }, []);
+
+  // Expose a refresh function via custom event
+  useEffect(() => {
+    const handler = () => {
+      listProjects().then(setProjects);
+    };
+    window.addEventListener("orchai:refresh-projects", handler);
+    return () => window.removeEventListener("orchai:refresh-projects", handler);
+  }, []);
+
+  return (
+    <aside className="w-64 bg-gray-900 text-gray-100 flex flex-col h-screen">
+      <div className="p-4 border-b border-gray-700">
+        <h1 className="text-lg font-bold">Orchai</h1>
+      </div>
+
+      <nav className="flex-1 overflow-y-auto p-2">
+        <div className="flex items-center justify-between px-2 py-1 mb-1">
+          <span className="text-xs font-semibold text-gray-400 uppercase tracking-wider">
+            Projects
+          </span>
+          <Link
+            to="/projects/new"
+            className="text-gray-400 hover:text-white text-lg leading-none"
+            title="Add project"
+          >
+            +
+          </Link>
+        </div>
+
+        {projects.map((project) => (
+          <Link
+            key={project.id}
+            to={`/projects/${project.id}`}
+            className={`block px-3 py-2 rounded text-sm ${
+              projectId === project.id
+                ? "bg-gray-700 text-white"
+                : "text-gray-300 hover:bg-gray-800 hover:text-white"
+            }`}
+          >
+            {project.name}
+          </Link>
+        ))}
+
+        {projects.length === 0 && (
+          <p className="px-3 py-2 text-sm text-gray-500">No projects yet</p>
+        )}
+      </nav>
+    </aside>
+  );
+}