Restructure into pnpm monorepo with game shell, docs, and SpacetimeDB backend

- Restructure flat static prototype into pnpm workspace monorepo
- apps/game: playable shell with R3F 3D scene, HUD, SpacetimeDB connection
- apps/docs: design docs and prototypes
- apps/site: landing page
- packages/ui: shared Button and Panel primitives
- services/spacetimedb: backend module (9 tables, 11 reducers)
- Archive legacy static files to archive/legacy-static/
- Game loop: connect, undock, target, approach, dock, mine, sell
- Add pnpm-workspace.yaml, tsconfig.base.json, spacetime.json

apps/docs/src/layouts/DocsLayout.tsx

@@ -0,0 +1,34 @@
+import { useState } from "react";
+import { Outlet, useLocation } from "react-router-dom";
+import { Sidebar } from "../components/Sidebar";
+import { TopBar } from "../components/TopBar";
+
+export function DocsLayout() {
+  const [collapsed, setCollapsed] = useState(false);
+  const { pathname } = useLocation();
+  const isFullscreenDemo = pathname.startsWith("/docs/demos/") || pathname.startsWith("/docs/prototypes/");
+
+  if (isFullscreenDemo) {
+    return (
+      <div className="flex h-screen w-full overflow-hidden bg-black max-md:block">
+        <div className="flex min-w-0 flex-1 flex-col overflow-hidden max-md:h-screen">
+          <div className="min-h-0 flex-1 overflow-auto overscroll-contain p-0">
+            <Outlet />
+          </div>
+        </div>
+      </div>
+    );
+  }
+
+  return (
+    <div className="flex h-screen w-full overflow-hidden max-md:flex-col">
+      <Sidebar collapsed={collapsed} />
+      <div className="flex min-w-0 flex-1 flex-col overflow-hidden max-md:min-h-0">
+        <TopBar collapsed={collapsed} onToggle={() => setCollapsed((value) => !value)} />
+        <div className="min-h-0 flex-1 overflow-y-auto overscroll-contain bg-bg px-10 py-8 max-md:px-5 max-md:py-4">
+          <Outlet />
+        </div>
+      </div>
+    </div>
+  );
+}