[lexical-playground] Bug Fix: restore RTL checkbox position in checklist

[ryanda9910]

Description

In RTL, the checklist checkbox renders on the wrong (left) side. v0.35.0 was reported as the cause, but tracing the CSS history shows the actual regression came from #7558, which reworked the checkbox marker to em-based units and, in the process, dropped the two [dir='rtl'] positioning overrides that used to mirror the marker to the right:

.PlaygroundEditorTheme__listItemUnchecked[dir='rtl']:before,
.PlaygroundEditorTheme__listItemChecked[dir='rtl']:before {
  left: auto;
  right: 0;
}

Since then the :before box and :after checkmark stay pinned to left, so the marker sits on the left in RTL.

Notably, the click hit-test in packages/lexical-list/src/checkList.ts already handles RTL correctly (it targets rect.right when target.dir === 'rtl'). So the marker was drawn on the left while the clickable area was on the right, i.e. the toggle target and the visible checkbox disagreed. Re-adding the RTL CSS overrides (mirrored to the right in the new em-based scheme) fixes the visual position and realigns it with the existing hit-test.

This is a minimal, CSS-only change scoped to the playground theme. The reporter also mentioned that the click logic expected left-side clicks, but that is no longer the case on main (RTL detection was added in #7429), so no plugin change is needed.

Closes #7929

Test plan

• pnpm vitest --project unit --no-watch packages/lexical-list/src/__tests__/unit/checkList.test.tsx -> 4/4 pass (no regression).
• prettier --check clean on the touched file.
• Visual verification of the em-based marker in RTL vs LTR (below). CSS positioning is not unit-testable; the checklist marker is not covered by the playground e2e in a way that asserts pixel side, so the device/e2e render is deferred to CI.

Before

RTL checkbox renders on the left (wrong).

After

RTL checkbox renders on the right (correct); LTR unchanged.

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Project	Deployment	Actions	Updated (UTC)
lexical	Ready	Preview	Jul 4, 2026 7:33am
lexical-playground	Ready	Preview	Jul 4, 2026 7:33am