Native TypeScript Toolsets for .opencode (code-first tools for subagents) #2237

Add a native TypeScript tool extension so subagents can mount code-defined tools from the repo (e.g., .opencode/tool/*.ts). This complements MCP (generic) and plugins (hooks) with a simple, typed, code-first path.

Problem
• Plugins = lifecycle hooks; MCP = service/protocol overhead.
• No first-class, TS-native way to ship repo-scoped tools with OpenCode context.

Proposal
• Support toolset: in subagent frontmatter to dynamically import a TS module exporting a ToolSet>.
• Tools run with OpenCode context via AsyncLocalStorage (eg. opencode.use()).
• Keep authoring aligned with AI SDK tool().

Subagent config (example)

---
description: Agent desc
mode: subagent
model: vercel/google/gemini-2.5-pro
temperature: 0.1
tools:
  write: true
  edit: true
  bash: true
  read: true
  grep: true
  glob: true
toolset: ./tool/my-agent-toolset.ts
---
You are a social media operator.

Tool module (example)

// ./tool/my-agent-toolset.ts
import { tool, type ToolSet } from 'ai';

const tools: ToolSet = { midjourney:tool({...}),  twitter_post: tool({   execute() {   opencode.use().calService()  } }) };
export default tools;