Missing <summary> tag silently drops all <param> customizations (short aliases, descriptions)

[Mpdreamz]

When a command's XML doc comment has <param> tags but no <summary> tag, every per-parameter customization encoded in those <param> tags — short aliases (-i, --in, ...) and descriptions — is silently dropped. The command still builds and runs fine, it just falls back to auto-generated kebab-case long names with no short alias and no description, as if the <param> tags weren't there at all.

This is silent: no generator diagnostic, no warning. I hit it while porting several tools off reflection-based CLI parsers (CommandLineParser/Argu) onto Nullean.Argh for AOT — for a while I assumed the difference was between registering via Map("name", MethodGroup) / MapRoot(MethodGroup) vs a class registered via Map<T>(), since that's what changed between my broken and working attempts. It isn't — it reproduces identically for both delegate-based and class-based registration, and for MapRoot too. The only variable that matters is whether <summary> is present.

Repro

Nullean.Argh 0.18.0, .NET SDK 10.0.300, macOS arm64.

using Nullean.Argh;

var app = new ArghApp();
app.Map<Commands>();

return await app.RunAsync(args);

public sealed class Commands
{
	/// <summary>Has a summary tag.</summary>
	/// <param name="input">-i, --in, Input path.</param>
	/// <param name="output">-o, --out, Output path.</param>
	[CommandName("with-summary")]
	public int WithSummary(string input, string output) => 0;

	/// <param name="input">-i, --in, Input path.</param>
	/// <param name="output">-o, --out, Output path.</param>
	[CommandName("without-summary")]
	public int WithoutSummary(string input, string output) => 0;
}

$ app with-summary --help
Usage: app with-summary --in <string> --out <string>

   Has a summary tag.

Options:
  -i, --in <string>   [required] Input path.
  -o, --out <string>  [required] Output path.

$ app without-summary --help
Usage: app without-summary --input <string> --output <string>

Options:
  --input <string>   [required]
  --output <string>  [required]

Both methods have byte-for-byte identical <param> tags. with-summary gets -i/-o short aliases and descriptions from them; without-summary gets neither, purely because it lacks a <summary> tag. Confirmed this holds for MapRoot(MethodGroup) too, not just Map<T>()/Map("name", MethodGroup).

Expected

<param> short-alias/description parsing shouldn't depend on <summary> being present — a command with no summary should still honor its parameter docs. Failing that, a generator diagnostic when <param> tags exist without a <summary> would at least surface the drop instead of silently falling back to defaults.