fix: use unsafeBitCast for thisObj in @JavaImplementation macro

In C++ interop mode, jobject is UnsafeMutablePointer<_jobject>, but
the swift-java library (compiled without C++ interop) expects jobject
as OpaquePointer. Use unsafeBitCast to ensure compatibility in both
modes since both have the same memory representation (a pointer).

This fixes the "cannot convert value of type 'jobject' to expected
argument type 'OpaquePointer'" error when building sample apps with
C++ interoperability enabled.

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

Co-Authored-By: Claude <[email protected]>

Author: NakaokaRei

Sources/SwiftJavaMacros/ImplementsJavaMacro.swift

@@ -128,8 +128,13 @@ extension JavaImplementationMacro: PeerMacro {
             return \(raw: tryClause)\(raw: swiftTypeName).\(raw: swiftName)(\(raw: swiftArguments.map { $0.description }.joined(separator: ", ")))\(raw: getJNIValue)
           """
       } else {
+        // Use unsafeBitCast to convert thisObj to OpaquePointer for C++ interoperability.
+        // In C++ mode, jobject is UnsafeMutablePointer<_jobject>, but the library
+        // (compiled without C++ interop) expects jobject as OpaquePointer.
+        // The bitcast ensures compatibility in both modes since both have the same
+        // memory representation (a pointer).
         innerBody = """
-            let obj = \(raw: swiftTypeName)(javaThis: thisObj, environment: environment!)
+            let obj = \(raw: swiftTypeName)(javaThis: unsafeBitCast(thisObj, to: OpaquePointer.self), environment: environment!)
             return \(raw: tryClause)obj.\(raw: swiftName)(\(raw: swiftArguments.map { $0.description }.joined(separator: ", ")))\(raw: getJNIValue)
           """
       }