feat(integration): add OAuth setup prompts - #2

Issue for this PR

Split from anomalyco#59456 (part 1 of 3).

Upstream review: anomalyco#59729.

Queued follow-ups: Vercel sign-in and key replacement. Each targets its dependency to keep the review diff focused.

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

OAuth sign-in can ask sequential, validated setup questions and return an optional completion link. The app, TUI, CLI, and Promise plugin adapter support the same attempt state. Authorization may produce an API key as well as OAuth credentials.

Includes cancellation, stale-step/retry handling, hidden field defaults, and duplicate-submission protection. No Vercel wizard, OAuth client ID, expiry monitoring, or credential replacement is included.

How did you verify your code works?

• Automated checks on this branch: 27 core tests, six app browser component tests, and 14 TUI tests passed.
• Regenerated the client.
• Full repository bun run check passed.

Manual verification covered the combined implementation: @pcomans tested setup and model availability on macOS before the split and before the temporary OAuth client ID was removed. This split PR has not been manually tested end to end.

Visual

<svg xmlns="http://www.w3.org/2000/svg" width="240" height="72" viewBox="0 0 240 72"><style>@media(prefers-reduced-motion:no-preference){.done{animation:pulse 3s infinite}}@keyframes pulse{0%,100%{opacity:.4}50%{opacity:1}}</style><g fill="none" stroke="currentColor" stroke-width="1.5"><rect x="4" y="14" width="62" height="44" rx="7"/><path d="M76 36h24m-6-6 6 6-6 6"/><rect x="108" y="14" width="62" height="44" rx="7"/><path d="M180 36h18m-6-6 6 6-6 6"/><circle cx="218" cy="36" r="16" opacity=".4"/><path class="done" d="m210 36 6 6 11-13"/></g><g fill="currentColor" font-family="sans-serif" font-size="9" text-anchor="middle"><text x="35" y="39">Sign in</text><text x="139" y="39">Setup</text></g></svg>

Screenshots / recordings

Setup-form and completion-link examples using fixture responses: gallery. The Vercel consumer is a separate follow-up.

Checklist

• Automated tests and checks passed locally on this branch
• I have not included unrelated changes in this PR