NavBar: layout does not switch to RTL for RTL locales #45

Problem

Selecting an RTL locale in NavBar translates the link labels but leaves the layout left-to-right. With ar selected in the docs demo:

• The logo stays on the left, links read left to right, and the language/GitHub/CTA group stays on the right.
• The language menu is pinned with a physical right-0 (src/registry/components/navbar.tsx:161), so it doesn't mirror.
• Option labels in the language menu render centered instead of start-aligned (the option <button> has no text-start, so the label inherits the button's default centering).

NavBar never sets dir. LanguageSwitcher already derives it from the active locale (activeLocale?.rtl ?? isRtl(locale)).

Expected

• NavBar sets dir="rtl" on the <nav> when the active locale is RTL, using the same rule as LanguageSwitcher (Locale.rtl override first, then isRtl from locale-data). An explicit dir prop wins.
• Layout mirrors via logical utilities: end-0/start-0 instead of right-0/left-0, ms-*/me-* instead of ml-*/mr-*, and text-start on option labels. This applies to the desktop bar, the mobile bar, the mobile menu and the language dropdown.
• Each option keeps its own dir, so mixed-script lists read correctly.

Acceptance

• Selecting ar flips the whole bar. Selecting en flips it back.
• Language dropdown opens aligned to the trigger's inline-end edge in both directions.
• Option labels are start-aligned in LTR and RTL.
• dir prop overrides the locale-derived direction.
• Tests for: dir on <nav> for an RTL locale, the Locale.rtl override (rtl: true / rtl: false), and the explicit dir prop.
• Screenshots: LTR and RTL, desktop and ~390px, light and dark.