feat: OpenCode Logging

[tolly-xyz]

Summary

• Add structured OpenCode plugin diagnostics via client.app.log()
• Log notable lifecycle events across STT, TTS, prompt loading, and LLM normalization
• Document how to use opencode’s own logs and --log-level for troubleshooting

Details

This change introduces a small shared logger wrapper around client.app.log() and threads it through the voice plugin so failures and state transitions are visible in OpenCode’s normal logs.
Logged areas include:

• Plugin initialization
• Custom prompt loading failures
• LLM normalization requests, responses, retries, and empty content cases
• STT recording, local whisper-cli execution, and STT API requests
• TTS normalization, Piper invocation, and SoX playback failures

Validation

• npm test
• npm run check

Notes

• Routine events log at debug
• Recoverable problems log at warn
• Failed child processes, API calls, and unexpected exceptions log at error

[tolly-xyz]

For context: I had some issues getting things set up for this plugin. Granted, I was not following the docs 1:1 (installed cli tools via nix-darwin), but having a view into the plugin's internal state would have made debugging things a lot easier. I did end up getting the plugin working, and I've really enjoyed using it!

[renjfk]

Hey, thanks for the contribution! I'm glad that it's been useful to folks other than me (:

There's one alarming conditional logic other than that it's fine.

[tolly-xyz]

Suggestion applied!