Package.swift declares iOS 11/12 minimum but code uses iOS 13+ concurrency features

[VictorPuga]

Description

OpenAPIKit's Package.swift declares iOS(.v11) (or iOS(.v12) in main) as the minimum platform, but the codebase uses Swift concurrency features (async/await) that require iOS 13.0 or later. This causes compiler errors when building projects that depend on OpenAPIKit.

Steps to Reproduce

1. Create a SwiftUI app targeting iOS 13.0+
2. Add OpenAPIKit 4.3.1 (or 5.2.1) as a dependency via SPM
3. Attempt to build the project

Expected Behavior

The build should succeed with the declared minimum platform.

Actual Behavior

Build fails with errors like:

Concurrency is only available in iOS 13.0.0 or newer
'isolation()' is only available in iOS 13.0 or newer
'withThrowingTaskGroup(of:returning:isolation:body:)' is only available in iOS 13.0 or newer

These errors appear across multiple files using async/await in both OpenAPIKit30 and OpenAPIKit targets.

Root Cause

The Package.swift declares iOS(.v11) or iOS(.v12) but the code uses async/await extensively without proper availability annotations.

Solution

Update Package.swift to declare the correct minimum iOS platform:

platforms: [
    .macOS(.v10_15),
    .iOS(.v13)  // Updated from .v11 or .v12
]