Add opencode support

[shanselman]

Can we make our install work with OpenCode?

Given https://gist.githubusercontent.com/xakpc/e8e10095733a445ed06fcc965c6f5d0a/raw/77efa28aa93d5692eca04e5d3e0f1be83d565220/toasty.js, also search the docs and plan how we'd add that support plus using an icon from somewhere in https://github.com/anomalyco/opencode

[shanselman]

Reopening: OpenCode (opencode-ai/opencode) currently has no plugin or hook system. The config schema only supports agents, providers, LSP, MCP servers, and TUI settings — no notification hooks. The JS plugin approach was based on incorrect/hallucinated documentation and has been removed. This issue should stay open until OpenCode adds a hook or notification mechanism upstream.