Support root selectors in stylis logical-properties middleware

Summary

Update createLogicalPropertiesMiddleware so it generates direction-scoped physical fallbacks for root selectors.

Required changes

In packages/stylis-logical-props-middleware/src/middleware.ts, apply the direction constraint directly to html and :root selectors. Continue to use the existing descendant-selector form for non-root selectors.

Rationale

The current generated selectors use a descendant combinator:

• html:not([dir=rtl]) html
• [dir=rtl] :root

These selectors cannot match the document root. As a result, logical declarations in html or :root rules do not receive physical fallbacks.

Affected area

• packages/stylis-logical-props-middleware/src/middleware.ts
• Middleware tests for logical-property fallback output

Acceptance criteria

• A rule with an html selector produces matching LTR and RTL fallback selectors.
• A rule with a :root selector produces matching LTR and RTL fallback selectors.
• Non-root selectors retain descendant-scoped LTR and RTL fallback behavior.
• Tests cover html, :root, and a non-root selector.

Backlinks

• Pull request: https://github.com/RocketChat/Rocket.Chat/pull/41861
• Review comment: https://github.com/RocketChat/Rocket.Chat/pull/41861#discussion_r3810310085

Requested by: @tassoevan