feat: 更新贡献昵称逻辑，允许用户留空昵称并调整相关测试用例

background.js

@@ -6619,7 +6619,7 @@ async function refreshOAuthUrlBeforeStep6(state) {
   if (state?.contributionMode && contributionOAuthManager?.startContributionFlow) {
     await addLog('步骤 7：contributionMode=true，走公开贡献接口，正在申请 OAuth 登录地址...', 'info');
     const contributionState = await contributionOAuthManager.startContributionFlow({
-      nickname: state.email,
+      nickname: state.contributionNickname || '',
       openAuthTab: false,
       stateOverride: state,
     });

background/contribution-oauth.js

@@ -247,9 +247,8 @@
 
     function buildNickname(state = {}, preferredNickname = '') {
       const nickname = normalizeString(preferredNickname)
-        || normalizeString(state.email)
         || normalizeString(state.contributionNickname);
-      return nickname || 'codex-extension-user';
+      return nickname || '';
     }
 
     function buildContributionQq(state = {}, preferredQq = '') {

sidepanel/sidepanel.html

@@ -112,7 +112,7 @@
         <p id="contribution-mode-text" class="contribution-mode-text">当前账号将用于支持项目维护。扩展会自动申请贡献登录地址并持续跟踪授权状态；如检测到回调地址，会自动提交，无需手动复制。</p>
         <div class="data-row contribution-mode-field">
           <span class="data-label">贡献昵称</span>
-          <input type="text" id="input-contribution-nickname" class="data-input" placeholder="可留空，默认使用当前邮箱" />
+          <input type="text" id="input-contribution-nickname" class="data-input" placeholder="可留空，将显示为匿名贡献者" />
         </div>
         <div class="data-row contribution-mode-field">
           <span class="data-label">QQ</span>

tests/background-contribution-mode.test.js

@@ -421,7 +421,7 @@ test('contribution oauth manager starts session, opens auth url, submits callbac
   assert.equal(startedState.contributionAuthTabId, 88);
   assert.equal(tabCalls.length, 1);
   assert.match(fetchCalls[0].url, /\/start$/);
-  assert.match(String(fetchCalls[0].options.body || ''), /"nickname":"user@example\.com"/);
+  assert.match(String(fetchCalls[0].options.body || ''), /"nickname":""/);
   assert.match(String(fetchCalls[0].options.body || ''), /"qq":""/);
   assert.match(fetchCalls[1].url, /\/status\?/);
 
@@ -511,7 +511,7 @@ return { refreshOAuthUrlBeforeStep6 };
     {
       type: 'contribution',
       options: {
-        nickname: 'user@example.com',
+        nickname: '',
         openAuthTab: false,
         stateOverride: {
           contributionMode: true,