Document @Generable macro visibility inside #Playground

[mattt]

Resolves #74

[Copilot]

Pull request overview

This PR documents a limitation where the memberwise initializer synthesized by the @Generable macro is not visible within other macro bodies like #Playground. This is due to how Swift macros compose—one macro's expansion isn't visible during another macro's body expansion.

Key Changes:

• Added documentation to the @Generable macro explaining the limitation and suggesting workarounds
• Added commented example code demonstrating two workaround approaches: using the init(_ generatedContent:) initializer directly and defining a factory method

Reviewed changes

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

File	Description
Sources/AnyLanguageModel/Generable.swift	Added doc comment with a note explaining that the synthesized memberwise initializer isn't visible inside other macro bodies and suggests workarounds
Tests/AnyLanguageModelTests/GenerableMacroTests.swift	Added conditionally-compiled example code demonstrating workarounds for using @Generable types within #Playground macros

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.