feat: add a JPMS module descriptor (io.github.dfa1.zstd)

- module-info.java exports the single public package. Lets modular
  consumers `requires io.github.dfa1.zstd` and scope native access with
  `--enable-native-access=io.github.dfa1.zstd` instead of ALL-UNNAMED.
- Suppress the module-name lint: the `dfa1` component ends in a digit
  (flagged as possibly version-like), but it mirrors the verified
  io.github.dfa1 namespace and the package, so keep it.
- NativeLibrary now loads the bundled library through the class loader
  (no leading slash) rather than Class#getResourceAsStream: the library
  lives in a separate zstd-native-<classifier> module and a named module
  only finds resources in itself. The classifier directory has a dash, so
  it is not a package and the resource is not module-encapsulated — the
  class loader reads it across modules and on the classpath alike.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: dfa1

zstd/src/main/java/io/github/dfa1/zstd/NativeLibrary.java

@@ -41,9 +41,14 @@ static MethodHandle lookup(String name, FunctionDescriptor fd) {
     private static String extractBundledLib() {
         String classifier = classifier();
         String ext = libExtension(classifier);
-        String resource = "/native/" + classifier + "/libzstd." + ext;
+        // Load through the class loader (no leading slash), not Class#getResourceAsStream:
+        // the library lives in a separate zstd-native-<classifier> module, and a named
+        // module only finds resources in itself. The classifier directory name contains a
+        // dash, so it is not a valid package and the resource is not module-encapsulated —
+        // the class loader can read it across modules (and on the classpath alike).
+        String resource = "native/" + classifier + "/libzstd." + ext;
 
-        try (InputStream in = NativeLibrary.class.getResourceAsStream(resource)) {
+        try (InputStream in = NativeLibrary.class.getClassLoader().getResourceAsStream(resource)) {
             if (in == null) {
                 throw new UnsatisfiedLinkError("No bundled zstd library found for platform " + classifier);
             }

zstd/src/main/java/module-info.java

@@ -0,0 +1,13 @@
+/// Java Foreign Function & Memory (FFM) bindings for Zstandard.
+///
+/// Exports the single public API package; the native `libzstd` is loaded at
+/// runtime from the platform `zstd-native-<classifier>` artifact on the path.
+/// Requires `--enable-native-access=io.github.dfa1.zstd` (or `ALL-UNNAMED` on
+/// the classpath) since FFM downcalls are a restricted operation.
+// The "dfa1" component ends in a digit, which the module-name lint flags as
+// possibly version-like. It mirrors the Sonatype-verified io.github.dfa1
+// namespace and the package name, so suppress the advisory rather than diverge.
+@SuppressWarnings("module")
+module io.github.dfa1.zstd {
+    exports io.github.dfa1.zstd;
+}