fix: handle empty covers and zero-valued close icons

[QDyanbing]

说明

• 按配置结构识别 preview cover，修复 cover=null、空配置和 coverNode 为零值或空值时的异常。
• 保留 closeIcon={0}；继续支持 true 使用默认图标、false/null 隐藏关闭按钮。
• 补充空封面、零值、元素/数组/Portal 封面以及关闭图标测试。

验证

• npm test -- --runInBand（93 项通过）
• npm run tsc
• 改动源码 ESLint 检查通过。

关联 ant-design/ant-design#59193

Summary by CodeRabbit

• Bug 修复
  • 修正图片封面内容的识别方式，并在未提供有效无障碍标签时使用替代文本。
  • 修正预览关闭按钮的图标显示：无法渲染的自定义图标将回退为默认图标。

[vercel]

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[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: b1f00e7d-cdb2-477b-99a4-df9f911576cf

📥 Commits

Reviewing files that changed from the base of the PR and between 4cbfa08 and 76e3d1c.

📒 Files selected for processing (3)

• src/Image.tsx
• src/Preview/index.tsx
• tests/renderability.test.tsx

Included review availability: This review used your included allowance. Your plan provides up to 2 included reviews per hour; 1 remain after this review.

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Walkthrough

本次调整封面对象的配置识别、预览状态下的 aria-label 回退，以及关闭图标的 React 可渲染性判断。新增测试覆盖封面值和关闭图标的渲染结果。

Changes

渲染值处理

Layer / File(s)	Summary
封面配置与预览标签 src/Image.tsx, tests/renderability.test.tsx	封面对象按 coverNode 或 placement 属性识别为配置；普通原型的空对象也识别为配置。配置的位置默认使用 center。预览状态下，aria-label 为 null 或 undefined 时回退到 alt。测试覆盖基本值、元素、数组和 portal。
关闭图标渲染 src/Preview/index.tsx, tests/renderability.test.tsx	仅当 closeIcon 不是 true 且可由 React 渲染时，才将其用作自定义图标，否则使用默认图标。测试覆盖按钮显示和图标内容。

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: afc163

Merge Risk: ⚪ Minimal · up to 76e3d

No actionable issue is established for the cover, preview-label, or close-icon changes; the PR is mergeable after normal checks.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	标题准确概括了主要变更：处理空封面，并保留零值关闭图标。标题简洁、明确，且与代码变更和 PR 目标一致。
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 3…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Commit to this branch
• Create a new PR

🧪 Generate unit tests (beta)

• Create a new PR

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_{兔子轻敲键盘忙，
封面节点逐个看。
小小图标选得准，
空值标签有回响。
测试排队把关强。}

_{Comment @coderabbitai help to get the list of available commands.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.26%. Comparing base (4cbfa08) to head (76e3d1c).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #534   +/-   ##
=======================================
  Coverage   99.26%   99.26%           
=======================================
  Files          17       17           
  Lines         543      546    +3     
  Branches      167      169    +2     
=======================================
+ Hits          539      542    +3     
  Misses          4        4           

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