Gets completion candidates for the specified tokenized command line.
public IEnumerable<string> GetCompletions(string? commandLine = null, string? commandName = null)
A partially typed command line, typically excluding the executable name (e.g. "hello --na").
If the executable name is included, it is ignored when it matches commandName or Name.
The invocation name (e.g. "mytool") to strip from the beginning of the token stream.
This API is intentionally non-executing: it does not invoke option actions. It only inspects the declared command tree.