Attach sidebar-close handler to current-page links

[jayaddison]

This is intended primarily to resolve a problem with singlehtml documentation projects when viewed on narrow (typically mobile) displays.

Under those circumstances, the .current CSS selector does not match any sidebar menu elements, because there is no logical notion of a 'current' page in singlehtml -- every item is on the same page.

Therefore this change proposes an alternative way to identify sidebar links that are 'current' -- it checks for anchors that have an href beginning with the query-string fragment identifier (#).

This is intended to be compatible with both singlehtml and html project builds. It depends upon sphinx-doc/sphinx#12551

Resolves #880.

[jayaddison]

Rebased against sphinx_rtd_theme v3.0.1, and rebuilt the theme.js file since previous commit -- no changes.

Test results when self-building the sphinx_rtd_theme documentation (in this repo) using Sphinx v8.1.3:

Before (buggy)

buggy.mp4

After (fixed)

fixed.mp4

[jayaddison]

Note: based on the dependency deprecation history for the project, I'd anticipate that the very earliest that this could be merged would likely be for a 4.0 release.

[jayaddison]

I'm uncomfortable with the way that I offensively dismissed what I felt to be a spammy issue request about AI in an unrelated FOSS project thread yesterday (2026-02-14). I mention this in case you'd prefer not to accept my contributions; however you are still welcome to. I don't use AI myself and would like not to be critical of those who do, but I was angry.