fix: resolve path canonicalization issue in acceptFolder on macOS/Windows

src/main/java/dev/jbang/devkitman/jdkproviders/BaseFoldersJdkProvider.java

@@ -4,6 +4,7 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.Objects;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Predicate;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -130,7 +131,35 @@ protected Stream<Path> listJdkPaths() throws IOException {
 	}
 
 	protected boolean acceptFolder(@NonNull Path jdkFolder) {
-		return jdkFolder.startsWith(jdksRoot) && JavaUtils.hasJavacCmd(jdkFolder);
+		return isUnderRoot(jdkFolder) && JavaUtils.hasJavacCmd(jdkFolder);
+	}
+
+	/**
+	 * Checks if the given path is under the jdksRoot directory. This method handles
+	 * the case where the paths may have different canonical forms (e.g. /var vs
+	 * /private/var on macOS) by falling back to toRealPath() comparison when a
+	 * simple startsWith check fails.
+	 */
+	protected boolean isUnderRoot(@NonNull Path jdkFolder) {
+		if (jdkFolder.startsWith(jdksRoot)) {
+			return true;
+		}
+		try {
+			return jdkFolder.toRealPath().startsWith(realJdksRoot());
+		} catch (IOException e) {
+			return false;
+		}
+	}
+
+	private final AtomicReference<Path> realJdksRootCache = new AtomicReference<>();
+
+	private Path realJdksRoot() throws IOException {
+		Path cached = realJdksRootCache.get();
+		if (cached == null) {
+			cached = jdksRoot.toRealPath();
+			realJdksRootCache.set(cached);
+		}
+		return cached;
 	}
 
 	private final Pattern validId = Pattern.compile("^[a-zA-Z0-9._+-]+$");

src/main/java/dev/jbang/devkitman/jdkproviders/DefaultJdkProvider.java

@@ -158,7 +158,7 @@ protected Path getJdkPath(@NonNull String id) {
 	}
 
 	protected boolean acceptFolder(@NonNull Path jdkFolder) {
-		if (!jdkFolder.equals(defaultJdkLink) && !jdkFolder.startsWith(jdksRoot)) {
+		if (!jdkFolder.equals(defaultJdkLink) && !isUnderRoot(jdkFolder)) {
 			return false;
 		}
 		String nm = jdkFolder.getFileName().toString();