feat(desktop): expose bot onboarding retry health

[testikun]

Summary

• Expose finite, redacted timeout/network/rate-limit/server retry health from the existing main-process Bot onboarding poll owner.
• Clear the projection on recovery, cancellation, expiry, denial, terminal failure, and supersession without changing retry thresholds, intervals, provider protocols, or persistence.
• Show concise localized backoff status in the existing QR onboarding modal while preserving the QR and secret-free IPC boundary.

Fixes #4745

Verification

• Core and Desktop focused onboarding tests: 22 passed.
• Redaction regressions: 27 passed.
• Electron retry-health E2E: 1 passed.
• Desktop build and typecheck.
• Core typecheck.
• Renderer architecture check.
• npm run lint.
• npm run format:check.
• npx knip --workspace apps/desktop.
• npm run check:asf-headers.
• git diff --check.

Visual evidence

Built and launched current head 3a37a66f3 in a visible local Electron App. The real QR onboarding modal kept the QR available while showing only the bounded retry category, consecutive count, and retry delay. This is a direct App capture, not a mockup or generated image.

The Electron test also asserts that fixture provider details do not appear in the renderer.

Review focus

The existing poll loop remains the only retry authority. retryHealth contains only a finite category, consecutive count, and retry timing; raw provider errors and credentials remain main-process-only.

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: OpenAI Codex implemented the bounded Core/Desktop contract, main-process projection, localized UI state, deterministic lifecycle/redaction coverage, and E2E visual fixture. The human contributor remains responsible for review and submission.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No