Closes: [BS-3485](https://linear.app/affine-design/issue/BS-3485/粘贴-html-格式的内容时，紧邻着-bold-text-的普通文本会丢失空格)
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## Summary by CodeRabbit
- **Bug Fixes**
- Improved handling of spaces and whitespace in paragraphs when converting HTML with inline formatting, ensuring spaces are preserved as in the original content.
- **Tests**
- Added a new test to verify that spaces are correctly preserved in paragraphs containing bold and italic formatting during HTML conversion.
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