chore(orbit): picker modal when multiple accounts match the link's server

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/store/orbitAccountPickerStore.ts

@@ -0,0 +1,39 @@
+import { create } from 'zustand';
+import type { ServerProfile } from './authStore';
+
+let _resolve: ((server: ServerProfile | null) => void) | null = null;
+
+interface OrbitAccountPickerStore {
+  isOpen: boolean;
+  accounts: ServerProfile[];
+  /** Open the picker with the given candidates. Resolves with the chosen
+   *  server or null if the user cancels. */
+  request: (accounts: ServerProfile[]) => Promise<ServerProfile | null>;
+  pick: (server: ServerProfile) => void;
+  cancel: () => void;
+}
+
+export const useOrbitAccountPickerStore = create<OrbitAccountPickerStore>(set => ({
+  isOpen: false,
+  accounts: [],
+
+  request: (accounts) =>
+    new Promise<ServerProfile | null>(resolve => {
+      // If another picker is already pending, treat the previous one as cancelled.
+      if (_resolve) _resolve(null);
+      _resolve = resolve;
+      set({ isOpen: true, accounts });
+    }),
+
+  pick: (server) => {
+    _resolve?.(server);
+    _resolve = null;
+    set({ isOpen: false });
+  },
+
+  cancel: () => {
+    _resolve?.(null);
+    _resolve = null;
+    set({ isOpen: false });
+  },
+}));