[OpenCode] Allow customizing the review agent name that feedback gets sent back to instead of `build`

[cb-bradbeebe]

Context

I started using Plannotator to review diffs and send feedback back to my OpenCode session, but I got an error in OpenCode's TUI that it could not find build agent. I have the build agent disabled in my opencode.json since I have a differently named one as my primary.

Request

Would you open to supporting a plugin option to define the build agent?

["@plannotator/opencode@latest", {
  "buildAgentName": "MyCustomAgentNameHere",
}]

Happy to submit a PR if you're aligned 👍

[backnotprop]

Thanks, real bug. Rather than a buildAgentName option, we'd like two changes in the plugin:

1. Default to no agent switch. Feedback goes back to whatever agent you were talking to (the agent param is optional).
2. If a name is set, validate it against client.app.agents() before sending. On a miss, fall back or omit, plus a warning toast. Today it fails silently.

PR welcome if you're still up for it. We'll fix the related Settings picker issues on our side.

[cb-bradbeebe]

@backnotprop

We'll fix the related Settings picker issues on our side.

Thanks! I had instinctively went there first to check if I could customize it so I imagine that'd help others as well.

---

we'd like two changes in the plugin:
PR welcome if you're still up for it.

Yup, aligned - I like that approach better, too.

[cb-bradbeebe]

@backnotprop PR ready for review: #1131

We'll fix the related Settings picker issues on our side.
FYI I addressed the issue with the Settings picker as since all these changes seemed best as a single unit than spread over different fixes.