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/components/TopBar.tsx

@@ -0,0 +1,37 @@
+import { Link, useLocation } from "react-router-dom";
+import { pageTitles } from "../data/nav";
+
+type TopBarProps = {
+  collapsed: boolean;
+  onToggle: () => void;
+};
+
+export function TopBar({ collapsed, onToggle }: TopBarProps) {
+  const location = useLocation();
+  const meta = pageTitles.get(location.pathname);
+  const section = meta?.section?.includes("Demo") || meta?.section?.includes("Prototype") ? "Demos" : "Docs";
+  const title = meta?.title ?? "Overview";
+
+  return (
+    <div className="flex h-topbar min-h-topbar min-w-0 items-center gap-4 border-b border-border bg-surface px-5 text-[0.8rem] max-md:gap-2 max-md:px-3">
+      <button
+        className="flex cursor-pointer items-center rounded border border-border bg-transparent px-2 py-1 text-base text-muted transition-all duration-150 hover:border-border-light hover:text-fg"
+        onClick={onToggle}
+      >
+        {collapsed ? "→" : "←"}
+      </button>
+      <div className="flex min-w-0 items-center gap-2 overflow-hidden whitespace-nowrap font-mono text-[0.75rem] text-muted max-md:flex-1">
+        <Link className="text-inherit no-underline" to="/">VOID::NAV</Link>
+        <span className="text-border-light">/</span>
+        <span>{section}</span>
+        <span className="text-border-light">/</span>
+        <span className="overflow-hidden text-ellipsis text-fg-bright">{title}</span>
+      </div>
+      <div className="ml-auto flex items-center gap-4 whitespace-nowrap font-mono text-[0.7rem] text-muted max-md:hidden">
+        <span><span className="mr-1 inline-block size-1.5 rounded-full bg-green shadow-[0_0_6px_var(--color-green)]" /> Connected</span>
+        <span className="text-accent">●</span>
+        <span>Prototype v0.1.0</span>
+      </div>
+    </div>
+  );
+}