Function init_logging 

pub fn init_logging(args: &Args) -> Result<Option<WorkerGuard>>

Initialize logging based on configuration arguments.

This function sets up tracing subscribers with:

• Environment-based log level filtering (falls back to args.log_level)
• Stderr output in text format (stdout is reserved for MCP protocol)
• Optional file logging with rotation support

Returns

• Ok(Some(WorkerGuard)) - File logging enabled, guard must be kept alive
• Ok(None) - No file logging configured
• Err(SshMcpError) - Configuration or IO error

Note

The WorkerGuard must be stored for the entire program lifetime when file logging is enabled, or the background worker will be dropped and logs may be lost.