Function write_cli_config 

pub fn write_cli_config(
    tool: CodeTool,
    temp_home: &Path,
    mcp_url: &str,
    session_id: &str,
    token: &str,
) -> Result<CliInjection, String>

Write the per-CLI MCP config under temp_home, returning any args that need to be appended to the command line.

This is the M3 per-CLI adapter. Each branch cites the source that documents the config location / mechanism so future maintainers can re-verify when the upstream CLI changes.