feat(docs): add dark-mode HTML styling and drop per-page ToC

- Add docs/html-style.html with Catppuccin Latte/Mocha palette,
  auto-selected via prefers-color-scheme
- Update html-docs workflow: embed stylesheet via --include-in-header,
  remove --toc so per-page sidebar is gone (index.html remains the ToC)
- Touch docs/fish-config.md to trigger the HTML generation workflow

fix(ci): clear docs/html/ before pandoc to avoid directory-exists error

fix(docs): restore toc on index, hide it on section pages via JS, fix
full-page bg

fix(docs): fix nav alignment by grouping label+link pairs as flex units

chore(docs): regenerate offline HTML docs

.gitea/workflows/html-docs.yml

@@ -25,7 +25,9 @@ jobs:
 
       - name: Generate chunked HTML docs
         run: |
-          pandoc -f gfm -t chunkedhtml --split-level=1 --toc -V toc=true \
+          rm -rf docs/html/
+          pandoc -f gfm -t chunkedhtml --split-level=1 --toc \
+                 --include-in-header docs/html-style.html \
                  docs/fish-config.md \
                  -o docs/html/