fix: wrong focus behavior when configuring menu selectability

[codewizardTM]

This PR fixes issue https://github.com/ant-design/ant-design/issues/53495

Determine the focus key based on the selectable configuration:

If the item is not selectable, focus the default item.

If the item is selectable, decide whether to focus based on whether there is already a selected item.

Summary by CodeRabbit

• Bug Fixes

  • 优化菜单组件焦点选择与聚焦行为：当支持可选项时优先聚焦已选项（若存在且有效），否则回退到活跃项或计算的默认焦点；当不支持可选项时始终使用计算的默认焦点，简化并统一聚焦优先级与回退逻辑。

• Tests

  • 新增针对可选/不可选场景的焦点交互测试，覆盖键盘导航与点击、聚焦顺序与 focus 调用验证。

[coderabbitai[bot]]

[!NOTE]

Other AI code review bot(s) detected

CodeRabbit has detected other AI code review bot(s) in this pull request and will avoid duplicating their findings in the review comments. This may lead to a less comprehensive review.

Walkthrough

修改 Menu 的聚焦与选中状态处理：引入并合并 select 键（internalSelectKeys / mergedSelectKeys），在 focus 流程中当 selectable 为 true 时优先聚焦首个选中键，否则尝试 mergedActiveKey，再回退到计算的默认焦点键；补充/调整相关单元测试覆盖行为。

Changes

Cohort / File(s)	变更摘要
菜单焦点与选中逻辑 src/Menu.tsx	引入内部 select 状态（internalSelectKeys）与合并键（mergedSelectKeys）；重构 useImperativeHandle 中的 focus 流程：当 selectable === true 时优先使用第一个有效的 select 键，失败则尝试 mergedActiveKey，最终回退到 defaultFocusKey；当 selectable === false 时直接使用 defaultFocusKey。移除重复的 select 状态声明并合并处理位置。
焦点行为测试 tests/Focus.spec.tsx	新增键盘事件辅助 keyDown（含 SubMenu 动画推进）并引入 KeyCode 与本地 isActive，添加两组测试验证在 selectable 为 false/true 时的聚焦与交互（DOWN/ENTER/点击）行为，通过 spy 检查元素 focus() 调用。

Sequence Diagram(s)

sequenceDiagram
  participant User as 用户
  participant Menu as Menu 组件
  participant Keys as 键来源器
  participant Focus as DOM.focus

  User->>Menu: 触发 menuRef.focus()
  Menu->>Keys: 计算候选焦点键
  alt selectable == true
    Keys->>Keys: 读取 mergedSelectKeys
    alt mergedSelectKeys 首项 有效
      Keys-->>Menu: 返回 mergedSelectKeys[0] (已选项)
    else
      Keys->>Keys: 检查 mergedActiveKey
      alt mergedActiveKey 有效
        Keys-->>Menu: 返回 mergedActiveKey
      else
        Keys-->>Menu: 返回 defaultFocusKey
      end
    end
  else selectable == false
    Keys-->>Menu: 返回 defaultFocusKey
  end
  Menu->>Focus: 对应元素调用 focus()
  Focus-->>Menu: 聚焦完成 / 抛出异常

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 分钟

Possibly related PRs

• react-component/menu#759 — 修改 menu 的 imperative handle（menuRef），添加了 findItem，可能与本次 focus/select 暴露的行为相互影响。
• react-component/menu#793 — 直接修改 src/Menu.tsx 中 select 状态与 focus 逻辑，与本次合并 select 键的变更高度相关。
• react-component/menu#791 — 也调整了 focus 选择逻辑（mergedActiveKey / fallback），与本次对 focus 决策路径的改动存在代码层面关联。

Suggested reviewers

• zombieJ
• afc163

诗

🐰 我是跳跃的小兔子，
先寻被选的那一只，
无果便望活跃位，
再无回首初始归，
菜单静好我来庆。

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title Check	✅ Passed	PR标题"fix: wrong focus behavior when configuring menu selectability"准确反映了本PR的主要变更。根据raw_summary，这个PR的核心是修复Menu组件的焦点行为，使其根据菜单的selectability配置进行条件判断：当selectable为false时焦点移到默认项，当selectable为true时焦点取决于是否有已选中的项。标题直接捕捉了这个核心改进，言简意赅且具体，避免了模糊措辞，使团队成员能够快速理解主要变更意图。

✨ Finishing touches

• [ ] 📝 Generate docstrings

🧪 Generate unit tests (beta)

• [ ] Create PR with unit tests
• [ ] Post copyable unit tests in a comment

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[gemini-code-assist[bot]]

Summary of Changes

Hello @codewizardTM, I'm Gemini Code Assist[^1]! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses and resolves an issue where the menu's focus behavior was incorrect, particularly when the selectable configuration was in use. The changes refine the focus determination logic to ensure that the appropriate menu item is focused based on whether the menu allows selection and if any items are already selected, thereby enhancing the user experience and consistency of the component.

Highlights

• Improved Focus Behavior: The logic for determining which menu item receives focus has been refactored to correctly account for the selectable property of the menu.
• Conditional Focus Application: When a menu is selectable, the focus will now only be applied if there are no items already selected, preventing unintended focus shifts.
• Default Focus Key: A defaultFocusKey variable has been introduced to consistently determine the fallback focus target, either the first focusable element or the first non-disabled child.
• Helper Function: A new helper function, getMergedSelectKeys(), was added to provide access to the current selection state within the focus logic.

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[codecov[bot]]

Codecov Report

:x: Patch coverage is 95.00000% with 1 line in your changes missing coverage. Please review. :white_check_mark: Project coverage is 99.59%. Comparing base (3ba3f98) to head (62360b5).

Files with missing lines	Patch %	Lines
src/Menu.tsx	95.00%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #818      +/-   ##
==========================================
- Coverage   99.72%   99.59%   -0.14%     
==========================================
  Files          26       26              
  Lines         727      733       +6     
  Branches      199      202       +3     
==========================================
+ Hits          725      730       +5     
- Misses          2        3       +1     

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[zombieJ]

@gemini-code-assist 请再次 CR

[zombieJ]

@gemini-code-assist 请完整的检测 PR 内容，并且对聚焦可能存在的 edge case 进行分析。

[codewizardTM]

@zombieJ 再帮忙 cr 一下