Fix scroll-padding-top not reaching live site (style.css/scss collision)

[lparsons]

Fixes #1483

Summary

• PR Offset in-page anchor jumps below the fixed navbar #2026 added assets/css/style.scss to set scroll-padding-top so in-page anchor jumps aren't hidden behind the fixed navbar. That merged cleanly and GitHub Pages rebuilt successfully, but the site already has a hand-maintained, statically-committed assets/css/style.css that Jekyll compiles/copies to the same output path (/assets/css/style.css).
• On GitHub's production build, the static style.css (12,262 lines of vendored/custom CSS) wins over the Sass-compiled style.scss, so the new rule silently never reached us-rse.org — no build error, just a destination-path collision.
• This PR moves the scroll-padding-top rule directly into assets/css/style.css (alongside the other hand-added custom rules at the end of the file) and removes the now-unnecessary style.scss.

Verified with a local bundle exec jekyll build: previously the compiled output only contained ~10 lines (the Sass file, since site.theme isn't set the @import pulled in nothing); now the full 12,262-line stylesheet is emitted with scroll-padding-top: 3.25rem; included.

Test plan

• bundle exec jekyll build succeeds
• Built assets/css/style.css contains the full existing stylesheet plus scroll-padding-top: 3.25rem;
• No .scss file remains to collide with the static .css at the same destination path

🤖 Generated with Claude Code

[lparsons]

@USRSE/usrse-maintainers This is a second attempt to fix the scrolling bug (#1483). I believe this will actually work, though it's a bit of a quick fix. Issue #2063 describes the larger issue. I'd recommend merging this fix and working on the larger refactor later.

[exoticDFT]

Looks good to me. The offset is working for a few pages I checked. Also, seems to work well enough for places where anchors have been manually added.