Document how to run a single accessibility test

[arturict]

Summary

• document how to pass a pytest -k expression through tox
• include a concrete command for running only test_search_as_you_type
• clarify that the focused environment expects assets and documentation to be built first

Closes #2092.

Validation

• confirmed the documented selector collects exactly test_search_as_you_type and deselects the other 35 accessibility tests
• documentation source check passed
• the Sphinx command generated the HTML, then exited non-zero in the warning-allowlist step because Graphviz dot is not installed locally
• git diff --check

Development note

Prepared with Codex assistance; validation performed is listed above.

[Yann-P]

Hello and thanks for you PR!

However, tox run -e a11y-tests won't work as is (try tox run -e a11y-tests -- --help, it is supposed to show pytest's help) but instead it just terminates with " congratulations :)" and no output

Because in tox.ini it is currently defined as [testenv:a11y-tests{-chromium,-firefox}] instead of [testenv:a11y-tests{,-chromium,-firefox}] which I believe is a mistake.

Only tox run -e a11y-tests-firefox and tox run -e a11y-tests-chromium work as is, and I believe docs/community/setup.md is wrong:

to run the tests without pre-compiling the assets and without re-building the docs (for example if you recently compiled the assets or built the docs)
tox run -e a11y-tests

The other criticism I have is that you document this specifically for accessibility tests, but -k is a pytest flag, so this is also true for all tests commands.

[Yann-P]

The way forward that I suggest:

• fix the tox.ini so that a11y-tests correctly default to a11y-tests-chromium
• make your documentation generic to all tests, not just accessibility tests

Also, I am unsure about the "search as you type" mentioned in the commit description, it doesn't work for me but maybe it's just my setup? I suggest to reword it without AI, I believe the AI added a lot of noise.