feat: improve the third-party provider configuration workflow

[1parado]

Issue for this PR

Closes # #2037

Type of change

• Bug fix
• New feature
• [√] Refactor / code improvement
• Documentation

What does this PR do?

• API-key-only authentication without OAuth.
• Support for OpenAI-compatible Chat Completions, OpenAI Responses, and Anthropic Messages.
• A paged provider setup wizard with back navigation.
• Model discovery through the provider's /models endpoint.
• Multi-select model configuration.
• Global provider deletion, including the stored API key and provider config.
• Updated documentation and generated SDK types for the new API.

How did you verify your code works?

• bun typecheck from packages/opencode
• bun test test/cli/provider-models.test.ts test/auth/auth.test.ts
• bun test test/config/config.test.ts
• bun test --timeout 15000 test/provider/provider.test.ts
• Prettier checks for the changed files

Screenshots / recordings

You can switch the configuration protocol.

You can automatically retrieve the list of available models.

verfy

v1/chat/completions

/v1/responses

/v1/messages

manage your third party provider

Checklist

• [√] I have tested my changes locally
• [√] I have not included unrelated changes in this PR

[1parado]

hi，@yanyihan-xiaomi. Please review the changes in this PR when you have time. Any feedback is welcome—I'll make the necessary updates. Thanks for your contributions to the open-source community!