* improved: better installation guide
- change `pip` to `{sys.executable} -m pip`
modified: To prevent the guide message from being obscured by a complex error message, apply `exit` instead of `raise`.
* ruff fix
* Frontend Manager: avoid redundant gh calls for static versions
* actually, removing old tmpdir isn't needed
I tested - downloader code handles this case well already
(also rmdir was wrong func anyway, needed shutil.rmtree if it had content)
* add code comment
* Add frontend manager
* Add tests
* nit
* Add unit test to github CI
* Fix path
* nit
* ignore
* Add logging
* Install test deps
* Remove 'stable' keyword support
* Update test
* Add web-root arg
* Rename web-root to front-end-root
* Add test on non-exist version number
* Use repo owner/name to replace hard coded provider list
* Inline cmd args
* nit
* Fix unit test
