[Enhancement]: support sidebar hmr

[SoonIter]

Version

rspress 1.38.0

Details

#1675

sidebar and title calculation is more complicated, hmr should be refactored

1. label in _meta.json

2. md h1 title

3. md frontmatter title

4. dir folder name

etc...

trigger siteMeta.json update from node side, and js side would reacted with hmr

Reproduce link

none

Reproduce Steps

none