feat(web): command palette, toasts, and global shell chrome

- CommandPalette (Alt+K): fuzzy action launcher with keyboard nav.
- Toasts: ephemeral notification stack + provider.
- useGlobalHotkeys: Alt+K palette toggle, G-chord navigation
  (G D/F/M/L/B/A/S/U/E/C), respects editable-element focus.
- Layout/App: wire ToastProvider at root, mount the palette inside the
  authed shell, introduce the global search box in the top bar.
- MazeNETRoute now renders TopologyList inline when no ?topology is
  present, instead of bouncing through a redirect.
- index.css: a few global token tweaks consumed by the new chrome.

Fixes a latent breakage: Config.tsx and MazeNET already imported
./Toasts/useToast but the directory was never committed.

decnet_web/src/hooks/useGlobalHotkeys.ts

@@ -0,0 +1,81 @@
+import { useEffect, useRef } from 'react';
+import { useNavigate } from 'react-router-dom';
+
+interface Options {
+  cmdOpen: boolean;
+  setCmdOpen: (v: boolean | ((prev: boolean) => boolean)) => void;
+}
+
+const G_NAV: Record<string, string> = {
+  d: '/',
+  f: '/fleet',
+  m: '/mazenet',
+  l: '/live-logs',
+  b: '/bounty',
+  a: '/attackers',
+  c: '/config',
+  s: '/swarm/hosts',
+  u: '/swarm-updates',
+  e: '/swarm/enroll',
+};
+
+const G_TIMEOUT_MS = 800;
+
+function isEditable(el: EventTarget | null): boolean {
+  if (!(el instanceof HTMLElement)) return false;
+  const tag = el.tagName;
+  return tag === 'INPUT' || tag === 'TEXTAREA' || el.isContentEditable;
+}
+
+export function useGlobalHotkeys({ cmdOpen, setCmdOpen }: Options): void {
+  const navigate = useNavigate();
+  const pendingG = useRef(false);
+  const gTimer = useRef<ReturnType<typeof setTimeout> | null>(null);
+
+  useEffect(() => {
+    const clearG = () => {
+      pendingG.current = false;
+      if (gTimer.current) { clearTimeout(gTimer.current); gTimer.current = null; }
+    };
+
+    const onKey = (e: KeyboardEvent) => {
+      if (e.altKey && e.key.toLowerCase() === 'k') {
+        e.preventDefault();
+        setCmdOpen(v => !v);
+        clearG();
+        return;
+      }
+
+      if (e.key === 'Escape' && cmdOpen) {
+        setCmdOpen(false);
+        clearG();
+        return;
+      }
+
+      if (cmdOpen) return;
+      if (isEditable(e.target)) return;
+      if (e.metaKey || e.ctrlKey || e.altKey) return;
+
+      const k = e.key.toLowerCase();
+
+      if (pendingG.current && G_NAV[k]) {
+        e.preventDefault();
+        navigate(G_NAV[k]);
+        clearG();
+        return;
+      }
+
+      if (k === 'g') {
+        pendingG.current = true;
+        if (gTimer.current) clearTimeout(gTimer.current);
+        gTimer.current = setTimeout(clearG, G_TIMEOUT_MS);
+      }
+    };
+
+    window.addEventListener('keydown', onKey);
+    return () => {
+      window.removeEventListener('keydown', onKey);
+      if (gTimer.current) clearTimeout(gTimer.current);
+    };
+  }, [cmdOpen, setCmdOpen, navigate]);
+}