a11y(downloads): native progressbar semantics + status announcements (#2342)

[kpoineal]

Summary

Fixes download progress in DownloadManager.tsx which was visual-only — only an �ria-label="NN%" on a plain

, which is insufficient for screen readers.

What changed

prototype/ui-redesign/src/components/DownloadManager.tsx (~line 283 / ~line 252):

1. Progress bar — replaced the bare

   with a proper
   ole="progressbar" element carrying �ria-valuenow, �ria-valuemin={0}, �ria-valuemax={100}, and an �ria-label that includes the model name (e.g. "Downloading Llama-3.1-8B: 42%"). The visual percentage text gets �ria-hidden="true" to prevent double-reading.

2. Status live region — added an always-present
   ole="status" aria-live="polite" aria-atomic="true" sr-only live region inside the panel. It announces status transitions only (start / complete / error / cancelled / paused / resumed) — never on every percentage tick. Clears when the panel closes to prevent stale announcements on reopen.

prototype/ui-redesign/tests/a11y.spec.ts — 4 new tests (A35–A38):

• A35:
  ole="progressbar" is present on the active download row
• A36: �ria-valuenow matches percent; �ria-valuemin=0; �ria-valuemax=100
• A37: �ria-label includes the model name
• A38: sr-only status live region is present when the panel is open

prototype/ui-redesign/ACCESSIBILITY.md — updated #2342 entry, test count table 34→38.

Note on prior work

fl0rianr's earlier �ria-label="NN%" was a good first step and showed the right intent. This PR extends it to the full ARIA progressbar pattern required by WCAG 4.1.2 and expected by NVDA/JAWS/VoiceOver.

Test result

54 passed, 7 skipped, 0 failed
(baseline was 50 passed / 7 skipped; +4 new a11y tests)

Closes #2342

A human reviewer should check the live-region announcement timing feels natural with an actual screen reader before merging.

[kpoineal]

Internal review: LGTM (advisory — human approval required)

Authored by Mattingly; reviewed by Lovell.

• DownloadManager.tsx ~line 326 — progressbar (a11y: Download progress is visual only #2342): role="progressbar" with aria-valuenow/aria-valuemin=0/aria-valuemax=100 and a model-name-qualified aria-label is the correct native ARIA pattern. Visual percentage <span> gets aria-hidden="true" — avoids double-reading. ✅
• Status live region: Always-present role="status" aria-live="polite" aria-atomic="true" .sr-only fires only on status transitions (start/complete/error/cancel/pause/resume), never on every percentage tick. prevStatusRef initialization skips spurious on-mount announcement. Cleared on isVisible=false to prevent stale re-reads on reopen. This is the correct implementation of the "announce transitions, not frames" requirement. ✅
• Tests A35–A38: A36 (exact aria-valuenow=42, aria-valuemin=0, aria-valuemax=100) is a strong structural assertion. A37 (model name in label). A38 verifies the live region is attached inside the panel. Per the documented test limitation, live region announcement content is not testable in Playwright without an AT driver — acceptable.
• DownloadStatus type now imported — diff confirms the import was added. ✅
• No behavior or visual regressions detected.

[kpoineal]

Rebased onto merged base a8718a7. Conflicts resolved in ests/a11y.spec.ts (branch's new tests renumbered to A59–A62) and ACCESSIBILITY.md (union merge). Final suite: 65 passed / 7 skipped / 0 failed. — Mattingly

[kpoineal]

Rebase round 2 — rebased onto \kpoin/ui-testing\ @ e0d1c92 (#2360 backend merged)

Conflicts resolved in \ ests/a11y.spec.ts\ and \ACCESSIBILITY.md\ by keeping both sides (base's A35–A45 presets + A51–A58 backend AND this branch's A59–A62 download tests). No renumbering needed — ranges already disjoint.

Final suite: 73 passed / 7 skipped / 0 failed

— Mattingly

[kpoineal]

Rebase round 3 complete — rebased onto \kpoin/ui-testing\ @ 7eb0c6c (post #2359 models merge).

Conflicts resolved by keeping both sides:

• \ ests/a11y.spec.ts: retained base A35–A58 (presets/models/backend) and this branch's A59–A62 (download progress bar). No renumbering.
• \ACCESSIBILITY.md: union-merged both sides' table rows and last-updated line.

Full suite result: 78 passed / 7 skipped / 0 failed. Branch force-pushed to \origin/feat/gui3-download-a11y.

— Mattingly

[fl0rianr]

LGTM