fix(vtable): update nested fields by path

[biubiukam]

🤔 This is a ...

• New feature
• Bug fix
• TypeScript definition update
• Bundle size optimization
• Performance optimization
• Enhancement feature
• Refactoring
• Update dependency
• Code style optimization
• Test Case
• Branch merge
• Site / documentation update
• Demo update
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🔗 Related issue link

fixes #4186

💡 Background and solution

changeFieldValue and changeFieldValueByRecordIndex treated nested FieldDef values as literal keys. For a field such as facts.2025-02.qty, the update therefore wrote record["facts.2025-02.qty"] instead of updating the nested quantity. The corresponding ListTable change events also read direct keys, so their old and changed values could be incorrect.

This change adds shared nested-field read and write handling for dotted paths and string[] paths. It preserves existing literal dotted-key precedence, creates missing intermediate objects, keeps numeric-string conversion behavior, and uses the same path resolution for hasField, column lookup, and change-event values.

Regression tests cover dotted and array paths, missing intermediate objects, literal-key precedence, and single/batch change-event payloads.

📝 Changelog

Language	Changelog
🇺🇸 English	Fix updates for nested fields represented by dotted or array paths, including accurate change-event values.
🇨🇳 Chinese	修复通过点号路径或数组路径更新嵌套字段，并确保变更事件中的新旧值准确。

☑️ Self-Check before Merge

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• TypeScript definition is updated/provided or not needed
• Changelog is provided or not needed

✅ Verification

• Focused regression tests: 2 suites, 12 tests passed, covering dotted and array paths plus single/batch event payloads.
• Full @visactor/vtable Jest suite: 75 suites, 326 tests passed.

🚀 Summary

copilot:summary

🔍 Walkthrough

copilot:walkthrough