Accessibility of the comment tree

Problem/Motivation

The rendered comment tree does not meet WCAG 2.1 A in several respects, and a partial tree is worse than no tree. The tree is partial (10 of N roots, lazy branches) but does not expose set size or position, has no accessible name, and comments have no headings. Other issues: no skip link, duplicated announcements, an aria-label on a generic div, and errors announced politely rather than assertively.

Steps to reproduce

• Open a thread with a screen reader.
• Traverse the tree: note a group of 216 announces as "1 of 10" with no set size or position.
• Attempt to bypass the comment block: no skip link exists.

Proposed resolution

• Add aria-setsize and aria-posinset to treeitems.
• Name the tree (role=tree) and each comment (role=heading or a heading element).
• Add a skip link before the comment block.
• Use role=alert for submission errors; avoid announcing to both Drupal.announce and the module's live region.
• Replace the aria-label on the generic status div with a semantic role.
• Do not point aria-describedby at the empty breadcrumb paragraph on root-level filter results, which currently leaves a dangling reference and adds dead vertical space per result.
• Use :focus rather than :focus-visible on the programmatically focused tabindex=-1 landing targets (.act-comment-approval and [data-act-pending]); :focus-visible generally does not match script-focused non-natively-focusable elements, so focus currently moves with no visible indicator after approving a comment.

Remaining tasks

• Verify with a screen reader and automated a11y checks.

User interface changes

Screen-reader-visible structure and announcements; no visual layout change.

API changes

None anticipated.

Data model changes

None anticipated.

AI-Generated: Yes (Used Opus 5 and DeepSeek Flash to review and discover these issues)