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/Sidebar.tsx

@@ -0,0 +1,68 @@
+import { NavLink } from "react-router-dom";
+import { navSections } from "../data/nav";
+
+type SidebarProps = {
+  collapsed: boolean;
+};
+
+export function Sidebar({ collapsed }: SidebarProps) {
+  return (
+    <aside
+      className={[
+        "z-10 flex h-screen flex-col overflow-hidden border-r border-border bg-surface transition-[width,min-width] duration-[250ms] max-md:h-auto max-md:max-h-[142px] max-md:w-full max-md:min-w-0 max-md:flex-shrink-0 max-md:border-r-0 max-md:border-b",
+        collapsed ? "w-sidebar-collapsed min-w-sidebar-collapsed max-md:w-full" : "w-sidebar min-w-sidebar",
+      ].join(" ")}
+    >
+      <div
+        className={[
+          "flex min-h-topbar items-center gap-3 border-b border-border px-5 py-4 max-md:min-h-[38px] max-md:justify-start max-md:px-4 max-md:py-2",
+          collapsed ? "justify-center px-4" : "",
+        ].join(" ")}
+      >
+        <div
+          className={[
+            "overflow-hidden whitespace-nowrap font-mono text-[0.8rem] font-bold uppercase tracking-[0.05em] text-accent max-md:text-[0.72rem]",
+            collapsed ? "text-0 max-md:text-[0.72rem]" : "",
+          ].join(" ")}
+        >
+          GDD<span className="text-cyan">::</span>DOCS
+        </div>
+      </div>
+      <nav
+        className={[
+          "flex-1 overflow-y-auto px-3 py-3 max-md:flex max-md:gap-2 max-md:overflow-x-auto max-md:overflow-y-hidden max-md:px-3 max-md:pb-3 max-md:pt-2",
+          collapsed ? "px-2 py-2" : "",
+        ].join(" ")}
+      >
+        {navSections.map((section) => (
+          <div key={section.title} className="max-md:flex max-md:flex-none max-md:gap-2">
+            <div
+              className={[
+                "overflow-hidden whitespace-nowrap px-3 pb-2 pt-4 font-mono text-[0.65rem] uppercase tracking-[0.1em] text-muted max-md:hidden",
+                collapsed ? "h-2 p-2 text-0" : "",
+              ].join(" ")}
+            >
+              {section.title}
+            </div>
+            {section.items.map((item) => (
+              <NavLink
+                key={item.path}
+                className={({ isActive }) =>
+                  [
+                    "mb-0.5 flex select-none items-center gap-3 overflow-hidden whitespace-nowrap rounded-lg px-3 py-2 text-[0.85rem] text-fg-dim no-underline transition-all duration-150 hover:bg-surface-raised hover:text-fg-bright max-md:mb-0 max-md:justify-start",
+                    collapsed ? "justify-center p-3 max-md:px-3 max-md:py-2" : "",
+                    isActive ? "border border-accent/25 bg-accent/8 text-accent" : "",
+                  ].join(" ")
+                }
+                to={item.path}
+              >
+                <span className="min-w-5 text-center text-base">{item.icon}</span>
+                <span className={collapsed ? "hidden max-md:inline" : ""}>{item.label}</span>
+              </NavLink>
+            ))}
+          </div>
+        ))}
+      </nav>
+    </aside>
+  );
+}