feat(remix): add toggle group

[leoafarias]

Summary

• add a complete, data-driven RemixToggleGroup<T> component backed by NakedToggleGroup<T>
• add group/item specs and stylers, selected/focused/disabled state styling, generated APIs, and a Fortal segmented-control recipe
• add a Widgetbook use case with orientation, loop, enabled, variant, size, and selection controls
• add component documentation and navigation
• add test helpers and a full pointer, keyboard, focus, RTL, disabled, loop/clamp, layout, spec, and style matrix

Why

Remix had standalone toggles but no single-select segmented-control component. Toggle Group provides one Tab stop, focus-only arrow navigation, explicit Space/Enter activation, orientation-aware movement, Home/End, disabled-item skipping, optional looping, and RTL-aware horizontal navigation.

Dependency note

The publishable dependency remains naked_ui: ^1.0.0-beta.3. A temporary dependency override tracks naked_ui main at d414875, where the roving-focus Toggle Group was merged in naked_ui PR #68. The override can return to a hosted version after the next naked_ui release.

Verification

• fvm dart run melos run ci --no-select
• generation check passed with no diff
• DCM passed with fatal style and warning checks
• demo package: 15 tests passed
• Remix package: 1,829 tests passed
• git diff --check origin/main...HEAD