Update swift-syntax version constraint to range 600.0.0..<603.0.0 (#5)

## Summary
Update swift-syntax dependency version constraint from `from: "602.0.0"`
to range `"600.0.0"..<"603.0.0"`.

Also update URL from deprecated `apple/swift-syntax` to the new
`swiftlang/swift-syntax`.

## Changes
- Modified Package.swift to use version range instead of minimum version
constraint
- Updated repository URL to the official Swift.org repository
- This allows compatibility with swift-syntax versions 600.0.0 through
602.x.x while excluding 603.0.0+

## Motivation
Range-based version constraints provide better compatibility and prevent
potential breaking changes from newer major versions while maintaining
support for a broader range of compatible versions.

## Testing
- [x] Package builds successfully with the new version constraint
- [x] All existing tests continue to pass

🤖 Generated with [Claude Code](https://claude.ai/code)

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: muukii

Package.swift

@@ -22,7 +22,7 @@ let package = Package(
     .package(url: "https://github.com/apple/swift-collections", from: "1.1.0"),
     .package(url: "https://github.com/VergeGroup/TypedComparator", from: "1.0.0"),
     .package(url: "https://github.com/VergeGroup/swift-typed-identifier", from: "2.0.4"),
-    .package(url: "https://github.com/apple/swift-syntax.git", from: "602.0.0"),
+    .package(url: "https://github.com/swiftlang/swift-syntax.git", "600.0.0"..<"603.0.0"),
     .package(url: "https://github.com/pointfreeco/swift-macro-testing.git", from: "0.2.1"),
   ],
   targets: [