Nominatim autocomplete missing ARIA combobox pattern (screen reader inaccessible)

Problem/Motivation

The Nominatim autocomplete (js/provider/nominatim-provider.js) builds a suggestions dropdown but does not implement the ARIA combobox pattern. As a result, screen reader users receive no indication that suggestions exist, cannot navigate them, and do not know which suggestion is active.

Specifically:

• The has no role="combobox", aria-expanded, aria-autocomplete, or aria-controls attributes
• The suggestions
  has no role="listbox"
• Each suggestion
• has no role="option" or id
• No aria-activedescendant is set on the input when navigating with arrow keys

This fails WCAG 2.1 success criteria 1.3.1 (Info and Relationships) and 4.1.2 (Name, Role, Value)

Steps to reproduce

1. Enable the module and add an EPS element to a webform with the Nominatim provider
2. Navigate to the form with a screen reader (NVDA + Firefox or VoiceOver + Safari)
3. Focus the search input and type at least 2 characters
4. Observe: the screen reader does not announce that suggestions appeared, and arrow key navigation is silent

Proposed resolution

Apply the ARIA combobox pattern (ARIA 1.2 combobox with listbox popup) to the Nominatim provider

Remaining tasks

• Apply the same fix to js/provider/google-places-provider.js (Google Places uses the browser's native autocomplete widget, which may already handle ARIA — needs verification)
• Manual test with NVDA + Firefox and VoiceOver + Safari