fix(core): report supported source version dynamically in annotation processor

[bercianor]

• Replace the fixed @SupportedSourceVersion(SourceVersion.RELEASE_8) declaration with a dynamic getSupportedSourceVersion() override.
• Make the annotation processor report the runtime JDK source level through SourceVersion.latestSupported().
• Eliminate the Java 25 warning about the processor supporting a lower source version than the build.