design: add catalog-backed settings search

[parsakhaz]

Context

Follow-up to #322. The settings redesign now has a typed catalog with category labels, descriptions, setting IDs, and aliases, but intentionally does not ship search in the first delivery.

Scope

• Search setting labels and descriptions.
• Search category names and catalog aliases.
• Group or label results by category.
• Selecting a result must use the typed settings target contract to navigate to the owning category.
• Scroll and focus the matched setting using its stable focus target.
• Preserve narrow-width keyboard behavior and modal focus trapping.
• Keep Remote Access workflow results capable of opening the appropriate typed subview.

Acceptance Criteria

• Search matches labels, descriptions, category names, and useful aliases without duplicating metadata outside the settings catalog.
• Results navigate through typed category, setting, and optional Remote Access subview targets.
• The selected setting is revealed, scrolled into view, and visibly focused.
• Empty, no-result, keyboard navigation, and Escape behavior are covered.
• Focused Playwright coverage includes normal and narrow settings layouts.

Blocked on / follows #322.