1. use grid instead of table, completely drop "ui table" from that list
2. move some "commit sign" related styles into a new file by the way (no
change) because I need to figure out where `#repo-files-table` is used.
3. move legacy "branch/tag selector" related code into repo-legacy.ts,
now there are 13 `import $` files left.
We have to define this one in helpers.css because tailwind only
generates a single class but certain things rely on this being
double-class. Command ran:
```sh
perl -p -i -e 's#gt-hidden#tw-hidden#g' web_src/js/**/* templates/**/* models/**/* web_src/css/**/*
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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>