refactor(cliproxy): address review feedback on parity and refresh flow

- make refresh ownership handling exhaustive in provider refresher

- extend backend/ui sync test to provider IDs and device-code providers

- remove DEFAULT_CURSOR_PORT re-export from use-cursor hook

- import cursor default port directly from shared defaults module

ui/src/hooks/use-cursor.ts

@@ -8,8 +8,6 @@ import { useMemo } from 'react';
 import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
 import { withApiBase } from '@/lib/api-client';
 
-export { DEFAULT_CURSOR_PORT } from '@/lib/default-ports';
-
 export interface CursorStatus {
   enabled: boolean;
   authenticated: boolean;

ui/src/pages/cursor.tsx

@@ -23,7 +23,8 @@ import {
   XCircle,
 } from 'lucide-react';
 import { cn } from '@/lib/utils';
-import { DEFAULT_CURSOR_PORT, useCursor } from '@/hooks/use-cursor';
+import { useCursor } from '@/hooks/use-cursor';
+import { DEFAULT_CURSOR_PORT } from '@/lib/default-ports';
 import { Button } from '@/components/ui/button';
 import { Input } from '@/components/ui/input';
 import { Label } from '@/components/ui/label';