[Docs] Add OpenCode Go Qwen3.8 Max guide

[zoomote]

​Opened on behalf of @taltas. Follow up by mentioning @roomote, in the web UI, or in Discord.

What changed

• Added OpenCode Go to the provider catalog.
• Documented subscription setup, API-key configuration, dynamic model refresh, and protocol selection.
• Documented Qwen3.8 Max context, output, multimodal, caching, and streamed reasoning behavior.
• Clarified that reasoning is displayed but not replayed across requests without a usable signed-thinking continuity field.

Why this change was made

The paired extension update adds native Qwen3.8 Max metadata for OpenCode Go. Users need a discoverable setup guide whose capability claims match the provider behavior available in Zoo Code.

Impact

Users can find OpenCode Go, configure Qwen3.8 Max, and understand the current reasoning-continuity limitation without relying on external setup details alone.

Related PRs

• Zoo-Code #1245

Screenshots

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Updated the paired guide in 8ed22a3 to describe streamed reasoning accurately and state that it is not replayed across requests without a usable signed-thinking continuity field.