local MCP server child processes become orphaned on restart #30073

Description

When opencode is restarted (e.g., during an update), its child MCP server
processes (configured as "local" type in opencode.json) are not always
killed. Over multiple restarts, orphan processes accumulate.

Steps to reproduce:

1. Configure a local MCP server (e.g., blender-mcp)
2. Restart opencode several times (e.g., via updates)
3. Observe that old MCP processes remain running: Get-Process blender-mcp
   shows multiple instances with different start times

Expected: MCP child processes are terminated when opencode exits.
Actual: Orphan processes are left running, potentially causing port conflicts
and resource leaks.

Suggested fix: On Windows, use a Job Object to bind child process lifetime
to the parent. On Unix, use process groups.

Plugins

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OpenCode version

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Steps to reproduce

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Screenshot and/or share link

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Operating System

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Terminal

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