Function resolve_shell 

pub fn resolve_shell(override_value: Option<String>, is_windows: bool) -> String

Decide which shell runs the rewritten command.

This used to be a hardcoded pwsh, which meant the tools/call path could not execute anything at all on Linux or macOS — PowerShell 7 is rarely installed there. Windows keeps pwsh so existing installs are unaffected; everywhere else falls back to sh. RTK_AGY_SHELL overrides both.