Merge main into v3: pick up v2 control-dock toggle…

Details

Brings in PRs #47 and #49 (v2 toggle hover labels: buttons expand with
one-word labels on hover, stay circular when collapsed, even expand/collapse;
and the gravity toggle label rename "Grid" -> "Gravity effect"). These touch
only frontend/jekyll/_sass/v2/_toggles.scss, which v3 never modifies, so the
merge is conflict-free. Keeps v3 a clean superset of main and brings the v2
page (now at /v2/) on the v3 preview up to date.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HShRpQUmDUttxD5F89ziDu

Files changed

Integration (merge) commit — no direct file changes.