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

tests/unit/cliproxy/backend-ui-default-ports-sync.test.ts

@@ -7,10 +7,22 @@
 import { describe, expect, test } from 'bun:test';
 import { CLIPROXY_DEFAULT_PORT as BACKEND_CLIPROXY_DEFAULT_PORT } from '../../../src/cliproxy/config/port-manager';
 import { DEFAULT_CURSOR_PORT as BACKEND_CURSOR_DEFAULT_PORT } from '../../../src/cursor/cursor-models';
+import {
+  CLIPROXY_PROVIDER_IDS as BACKEND_CLIPROXY_PROVIDER_IDS,
+  getProvidersByOAuthFlow,
+} from '../../../src/cliproxy/provider-capabilities';
 import {
   CLIPROXY_DEFAULT_PORT as UI_CLIPROXY_DEFAULT_PORT,
   DEFAULT_CURSOR_PORT as UI_CURSOR_DEFAULT_PORT,
 } from '../../../ui/src/lib/default-ports';
+import {
+  CLIPROXY_PROVIDERS as UI_CLIPROXY_PROVIDERS,
+  DEVICE_CODE_PROVIDERS as UI_DEVICE_CODE_PROVIDERS,
+} from '../../../ui/src/lib/provider-config';
+
+function sorted(values: readonly string[]): string[] {
+  return [...values].sort((a, b) => a.localeCompare(b));
+}
 
 describe('Default Port Sync', () => {
   test('CLIProxy default port is synced between backend and UI', () => {
@@ -20,4 +32,12 @@ describe('Default Port Sync', () => {
   test('Cursor default port is synced between backend and UI', () => {
     expect(UI_CURSOR_DEFAULT_PORT).toBe(BACKEND_CURSOR_DEFAULT_PORT);
   });
+
+  test('CLIProxy provider IDs are synced between backend and UI', () => {
+    expect(sorted(UI_CLIPROXY_PROVIDERS)).toEqual(sorted(BACKEND_CLIPROXY_PROVIDER_IDS));
+  });
+
+  test('Device code providers are synced between backend and UI', () => {
+    expect(sorted(UI_DEVICE_CODE_PROVIDERS)).toEqual(sorted(getProvidersByOAuthFlow('device_code')));
+  });
 });