feat(control): grid snap, NPC context actions, and overlay dim fix

Re-enable users-branch UI, snap session tokens to square/hex grid from the control preview, refine inactive/open-info NPC menus, block marker actions while an effect brush is active, and dim materials/NPC overlays only when they are open.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/renderer/shared/tokens/useTokenGridSnapSession.ts

@@ -0,0 +1,33 @@
+import { useCallback, useEffect, useState } from 'react';
+
+import { ipcChannels } from '../../../shared/ipc/contracts';
+import { getDndApi } from '../dndApi';
+
+export function useTokenGridSnapSession(): [
+  boolean,
+  { setEnabled: (enabled: boolean) => Promise<boolean> },
+] {
+  const api = getDndApi();
+  const [enabled, setEnabledState] = useState(false);
+
+  useEffect(() => {
+    void api.invoke(ipcChannels.tokenGridSnap.getState, {}).then((res) => {
+      setEnabledState(Boolean(res.enabled));
+    });
+    return api.on(ipcChannels.tokenGridSnap.stateChanged, ({ enabled: next }) => {
+      setEnabledState(Boolean(next));
+    });
+  }, [api]);
+
+  const setEnabled = useCallback(
+    async (next: boolean) => {
+      setEnabledState(next);
+      const res = await api.invoke(ipcChannels.tokenGridSnap.setEnabled, { enabled: next });
+      setEnabledState(Boolean(res.enabled));
+      return Boolean(res.enabled);
+    },
+    [api],
+  );
+
+  return [enabled, { setEnabled }];
+}