[FEATURE]: Add Poe as a built-in auth provider

[kamilio]

Feature hasn't been suggested before.

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Describe the enhancement you want to request

Poe (poe.com) is an AI platform that provides access to various models through a unified API. Currently, OpenCode supports Codex, Copilot, and GitLab as built-in auth plugins but does not support Poe.

Adding Poe as a built-in auth plugin would allow users to authenticate via browser-based OAuth (PKCE flow) or manually enter an API key, similar to how the existing Codex plugin works. This lets users access models on Poe directly through OpenCode without manual configuration.

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Proposal: Support poe.com as an LLM provider #1788: Previous proposal to support poe.com as an LLM provider (closed)
• Poe as a model provider has stopped working #17302: Poe as a model provider has stopped working — suggests Poe is already partially supported as a provider

If Poe already works as a custom provider and this is specifically about adding first-class OAuth/PKCE auth plugin support (similar to Codex/Copilot), please clarify how this differs from the existing support shown in #17302.

[kamilio]

Hi, I work on Poe, and we just launched OAuth. As a big opencode fan, I thought it would be nice to include it and make it easy for our users to connect Poe as a provider.

I didn't find this specific feature