"shell": "pwsh" config not respected, still uses PowerShell 5.1 on Windows #30615

Description

Bug Description
The shell setting in opencode.json is set to "pwsh" but opencode still uses PowerShell 5.1 (powershell.exe) as the default shell.

Config
~/.config/opencode/opencode.json:

{
"$schema": "https://opencode.ai/config.json",
"shell": "pwsh",
"provider": {}
}
Actual Behavior
Running commands through the bash tool executes in PowerShell 5.1:

PSVersion: 5.1.26100.8457
ProcessName: powershell
Path: C:\WINDOWS\System32\WindowsPowerShell\v1.0\powershell.EXE
Expected Behavior
When "shell": "pwsh" is configured, commands should execute in PowerShell 7 (pwsh.exe), which defaults to UTF-8 and resolves Chinese encoding issues that plague PS 5.1.

Environment
OS: Windows (win32)
PowerShell 5.1: C:\WINDOWS\System32\WindowsPowerShell\v1.0\powershell.EXE
PowerShell 7: installed and available at pwsh
opencode config: ~/.config/opencode/opencode.json with "shell": "pwsh"
Impact
Chinese (and other non-ASCII) characters are garbled in PS 5.1 due to GB2312 default encoding. PS 7 uses UTF-8 by default and works correctly.

Plugins

No response

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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