OpenCode 0.15 is out and may support the events / notifications Scion needs to be more fully integrated

[verdverm]

Problem / Motivation

OpenCode is incomplete

Proposed Solution

OpenCode can be fully Scion featured

Additional Context

https://github.com/anomalyco/opencode/releases/tag/v1.15.0

Two notable entries from the release notes

• Added an Effect-based core event system for more complete event delivery across sessions and integrations.
• Restored missing event types in the JavaScript SDK, including session and message events.

I do wonder if we need/can make OpenCode more Scion friendly with a custom plugin: https://opencode.ai/docs/plugins/#events

I will be looking into this over the weekend, will report findings and progress here. I have a couple of small PRs here to address a couple gaps I worked through.

[verdverm]

I've started a discussion here: #252