Title: Accessibility: Slash-command popup menu options are hidden from screen readers (missing listbox/option roles and active descendant link)

Summary

The desktop app's chat input field has a slash-command autocomplete/suggestion popup menu. While it is visually rendered correctly, it is completely hidden from Windows UI Automation and screen readers (like NVDA or JAWS). Users relying on screen readers receive no feedback when typing / and cannot read or navigate the options using the arrow keys.

Diagnostic Details

We probed the application using the Chromium DevTools Protocol (CDP) accessibility domain (Accessibility.getFullAXTree) and observed the following:

1. Role Mismatch:
   The slash-command list items (e.g., /init, /review, or custom skills) are exposed to the accessibility tree as standard unassociated buttons (role="button") instead of list items.
2. Missing Container & Attributes:
   There is no parent wrapper acting as a role="listbox" to group these options.
3. No Active Descendant Linking:
   When the user navigates through the suggestions using the Up/Down arrow keys, keyboard focus remains on the main text input field. There is no aria-controls on the input element pointing to the listbox, nor is there an aria-activedescendant attribute updated dynamically on the input element to announce the currently highlighted option to assistive technologies.

Expected Behavior

1. The container enclosing the slash commands list should have role="listbox".
2. Each item in the suggestion list should have role="option" and update its aria-selected state dynamically.
3. The chat input text element should have aria-haspopup="listbox", aria-controls="[listbox-id]" (pointing to the dropdown container), and aria-activedescendant="[active-option-id]" which dynamically tracks the ID of the highlighted menu item as the user presses Arrow Up/Down.

Screenshots / Logs

We verified that when the suggestion menu is open, the AX tree output is populated with buttons but lacks standard dropdown structure:

// Example node found in the AX Tree during CDP accessibility probe:
{
  "role": "button",
  "name": "/init guided AGENTS.md setup",
  "ignored": false
}

This prevents Windows UIA and screen readers from capturing tree-change events on arrow-key navigation.