Fix option construction

[gewarren]

Fixes #50368

Th previous code throws a runtime exception due to the breaking change noted in the second paragraph here.

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Internal previews

📄 File	🔗 Preview link
docs/standard/commandline/how-to-parse-and-invoke.md	Parsing and invocation in System.CommandLine

[Copilot]

Pull request overview

This PR addresses issue #50368 by updating code to comply with breaking changes introduced in System.CommandLine 2.0.0-beta5, specifically related to option construction syntax.

• Updates the Option<T> constructor usage to use object initializer syntax for setting the Description property, as the two-parameter constructor accepting description is no longer supported.
• Modernizes API references in documentation by correcting namespaces (e.g., System.CommandLine.ParseResult instead of System.CommandLine.Parsing.ParseResult) and adding proper cross-references.
• Improves documentation formatting by adding code-style backticks to type names in headings, consistent with .NET documentation standards.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
docs/standard/commandline/snippets/handle-termination/csharp/Program.cs	Updates option construction to use object initializer syntax for Description property instead of constructor parameter.
docs/standard/commandline/how-to-parse-and-invoke.md	Corrects API namespaces, adds proper xref links for types and methods, improves code formatting in headings, and simplifies inline method references for better readability.