Reformat pkgdown workflow

[VisruthSK]

• Build site in master to .\docs
• GitHub Action builds site on releases (double check to ensure Action doesn't wipe root and replace with static files)
• Updated favicons

The repo's Pages settings will have to be updated to point towards the master branch and .\docs

Note that the site is built with Bootstrap 3 which has been deprecated for a while. Swapping to Bootstrap 5 would require some SCSS/CSS to maintain the exact theme, or a coordinated change of themes from all Stan pkgdown sites (probably through a template package). This PR doesn't attemp to further either goal, and sticks with the usual Bootstrap 3 and Cosmo from Bootswatch 3.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.54%. Comparing base (9886905) to head (7235e08).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #292   +/-   ##
=======================================
  Coverage   92.54%   92.54%           
=======================================
  Files          31       31           
  Lines        3018     3018           
=======================================
  Hits         2793     2793           
  Misses        225      225           

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[VisruthSK]

On second though, if possible, it might make more sense to automatically build and deploy sites to https://dev.mc-stan.org/loo/ and setup another workflow to generate the site on releases which would get pushed to https://mc-stan.org/loo/.

[VisruthSK]

on:
pull_request:
should be removed once the workflow is confirmed to work.

Obviated

[jgabry]

On second though, if possible, it might make more sense to automatically build and deploy sites to https://dev.mc-stan.org/loo/ and setup another workflow to generate the site on releases which would get pushed to https://mc-stan.org/loo/.

Yeah I agree that it would be preferable to only publish the site on https://mc-stan.org/loo/ when we do a release. If we publish at the main URL on every commit to master then the website could advertise unreleased features that aren't available on CRAN yet.

[jgabry]

I think this looks good. But the regenerated website pages that are part of this PR are for the development version of loo, not the released version. So if I merge this won't it update the website to the development version?

[VisruthSK]

Right, I'll move files from the gh-pages branch into the docs folder then

[VisruthSK]

https://github.com/stan-dev/loo/actions/runs/15627201098/job/44023603976

Looks like the vignettes get built too.