Fix: Add registerMenu method to FoundryAdapter

Added missing registerMenu method to the settings surface of FoundryAdapter
to support GM Player Privacy Selector menu registration.

This fixes the error: TypeError: _adapter.settings.registerMenu is not a function

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

src/foundry/FoundryAdapter.js

@@ -67,6 +67,8 @@ export class FoundryAdapter {
       get: (key) => g.settings?.get(ns, key) ?? null,
       /** @param {string} key @param {unknown} value @returns {Promise<unknown>} */
       set: (key, value) => /** @type {Promise<unknown>} */ (g.settings?.set(ns, key, value) ?? Promise.resolve()),
+      /** @param {string} namespace @param {string} menuKey @param {object} config */
+      registerMenu: (namespace, menuKey, config) => g.settings?.registerMenu(namespace, menuKey, config),
     };
 
     /** Socket surface — wraps game.socket. */