Davy7/26/2026, 2:03:33 AM

First separation on a fresh install pulled the reduced ONNX Runtime in
the background, but the UI only showed "Separating 0%" with no labeled
task, so it looked frozen for several seconds (longer on weak networks) —
the first suspected failure a new user hits.

- runtime_bootstrap: emit RUNTIME_BOOTSTRAP_PROGRESS_EVENT during the
  download via a new report_download_progress helper (mirrors the model
  bootstrap progress pattern) so the frontend tracks bytes live instead
  of only receiving the initial 0% snapshot. Covers both the first-install
  and candidate/update download paths.
- GlobalProgressBar: add a named "Downloading runtime" task driven by the
  runtime bootstrap store (downloading + downloading_candidate).
- RuntimeUpdateBanner: cover Missing/Downloading/Failed, with Failed
  retryable via download_runtime (same recovery pattern as the #217
  ModelBootstrapBanner).
- i18n: add en/zh-CN keys and a bootstrap-banner i18n completeness guard.

Tests: backend unit test for the new progress emit; component tests for
the runtime progress task and the Failed-banner retry.

Fixes #226

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

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