时间展示希望能支持自定义格式

**What problem does this feature solve? (这个功能解决了什么问题)**
目前时间的展示最近的消息会被解析成星期几/昨天。不能明确具体日期。希望能展示具体的日期
**Describe the solution you'd like (描述您想要的解决方案)**

**What does the proposed API look like? (你期望的 API 是怎样的)**

No file, test, or entry point is named. Start by locating the message-time rendering component and its existing weekday/yesterday formatting; clarify the custom-format API and concrete-date behavior, then add coverage showing the requested date display.

Written by the indexing model from the issue text.