feat(web): add ? cheatsheet and / focus-search hotkeys

- New ShortcutsHelp modal enumerates global, nav G-chord and palette
  bindings; openable via ? (Shift+/) or the command palette.
- / dispatches a global decnet:focus-search event; Attackers, Bounty
  and LiveLogs listen and focus their in-page search inputs (pages
  without a local search are skipped per plan).
- Respects the existing editable-element guard and Alt+K palette
  toggle; no rebinds to prior shortcuts.

decnet_web/src/hooks/useGlobalHotkeys.ts

@@ -4,6 +4,8 @@ import { useNavigate } from 'react-router-dom';
 interface Options {
   cmdOpen: boolean;
   setCmdOpen: (v: boolean | ((prev: boolean) => boolean)) => void;
+  helpOpen: boolean;
+  setHelpOpen: (v: boolean | ((prev: boolean) => boolean)) => void;
 }
 
 const G_NAV: Record<string, string> = {
@@ -27,7 +29,7 @@ function isEditable(el: EventTarget | null): boolean {
   return tag === 'INPUT' || tag === 'TEXTAREA' || el.isContentEditable;
 }
 
-export function useGlobalHotkeys({ cmdOpen, setCmdOpen }: Options): void {
+export function useGlobalHotkeys({ cmdOpen, setCmdOpen, helpOpen, setHelpOpen }: Options): void {
   const navigate = useNavigate();
   const pendingG = useRef(false);
   const gTimer = useRef<ReturnType<typeof setTimeout> | null>(null);
@@ -52,10 +54,26 @@ export function useGlobalHotkeys({ cmdOpen, setCmdOpen }: Options): void {
         return;
       }
 
-      if (cmdOpen) return;
+      if (cmdOpen || helpOpen) return;
       if (isEditable(e.target)) return;
       if (e.metaKey || e.ctrlKey || e.altKey) return;
 
+      // `?` (Shift+/) — open shortcuts cheatsheet
+      if (e.key === '?') {
+        e.preventDefault();
+        setHelpOpen(true);
+        clearG();
+        return;
+      }
+
+      // `/` — focus page search (page listens for the event)
+      if (e.key === '/') {
+        e.preventDefault();
+        window.dispatchEvent(new CustomEvent('decnet:focus-search'));
+        clearG();
+        return;
+      }
+
       const k = e.key.toLowerCase();
 
       if (pendingG.current && G_NAV[k]) {
@@ -77,5 +95,5 @@ export function useGlobalHotkeys({ cmdOpen, setCmdOpen }: Options): void {
       window.removeEventListener('keydown', onKey);
       if (gTimer.current) clearTimeout(gTimer.current);
     };
-  }, [cmdOpen, setCmdOpen, navigate]);
+  }, [cmdOpen, setCmdOpen, helpOpen, setHelpOpen, navigate]);
 }