Clarify difference between type annotation and type test patterns in F# documentation

[Copilot]

• Understand the current documentation structure
• Review the examples provided by the subject matter expert
• Enhance the "Patterns That Have Type Annotations" section with better explanation
• Enhance the "Type Test Pattern" section with better explanation and contrast
• Add contrasting examples that clearly show the difference
• Test that all code examples compile correctly
• Apply code review suggestions (formatting and lint fixes)
• Add ai-usage frontmatter metadata

Summary of Changes

Enhanced the F# pattern matching documentation to clearly contrast between:

1. Pattern That Has Type Annotation (pattern : type):

   • Added explanation that it provides compile-time type information
   • Clarified it doesn't perform runtime type checking
   • Added key characteristics list

2. Type Test Pattern (:? type):

   • Added explanation that it performs runtime type checking
   • Clarified similarity to C#'s is or as operators
   • Added key characteristics list

3. New Contrasting Section:

   • Added a comparison table showing syntax, timing, purpose, and C# equivalents
   • Included side-by-side code examples demonstrating the difference
   • Made it clear that type annotation is compile-time while type test is runtime

All code examples have been verified to compile successfully with F# 9.0.

Applied formatting fixes per code review and added required ai-usage: ai-assisted frontmatter metadata.

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Internal previews

📄 File	🔗 Preview link
docs/fsharp/language-reference/pattern-matching.md	docs/fsharp/language-reference/pattern-matching

[BillWagner]

This is ready once I apply suggestions

[Copilot]

Pull Request Overview

This PR clarifies the distinction between type annotation patterns and type test patterns in F# pattern matching documentation. These syntactically similar patterns serve fundamentally different purposes—compile-time type inference vs. runtime type checking—which was causing reader confusion.

Key changes:

• Enhanced explanations for both pattern types with clear compile-time vs. runtime distinctions
• Added a new comparison section with side-by-side examples and a feature comparison table
• Added C# equivalents to make concepts more accessible to developers from other .NET languages

[Copilot]

This is ready once I apply suggestions

All suggestions have been applied in commit e0e0ee0.

[IEvangelist]

Missing frontmatter/metadata.

[Copilot]

Missing frontmatter/metadata.

Added ai-usage: ai-assisted frontmatter in commit 7f8a73e.