refactor(java): simplify loader-unification code

- MetaDataLoader.fromUris: replace stream/Collectors with a plain
  for-loop over an ArrayList sized from the input, matching the
  existing style in loadSourceURIsIfPresent / fromResources /
  processSources in the same file.
- MetaDataLoader: drop the now-unused java.util.stream.Collectors
  import that was only there for fromUris.
- MetaDataSource Javadoc: extend the "Concrete implementations" list
  and @see block to include the new FileSource and DirectorySource
  classes added in this branch (the list previously only mentioned
  InMemoryStringSource and UriSource).

No behavior changes; full reactor mvn test passes (17/17 modules).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: dmealing

server/java/metadata/src/main/java/com/metaobjects/loader/MetaDataLoader.java

@@ -32,7 +32,6 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
-import java.util.stream.Collectors;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutionException;
@@ -238,9 +237,8 @@ public static MetaDataLoader fromUris(String name, List<URI> uris) {
         MetaDataLoader loader = createManual(false, name);
         try {
             loader.init();
-            List<MetaDataSource> sources = uris.stream()
-                .map(uri -> (MetaDataSource) new UriSource(uri))
-                .collect(Collectors.toList());
+            List<MetaDataSource> sources = new ArrayList<>(uris.size());
+            for (URI uri : uris) sources.add(new UriSource(uri));
             loader.load(sources);
             loader.register();
         } catch (MetaDataLoadingException e) {

server/java/metadata/src/main/java/com/metaobjects/loader/MetaDataSource.java

@@ -12,11 +12,15 @@
  * <p>Concrete implementations:
  * <ul>
  *   <li>{@link InMemoryStringSource} — a pre-loaded string (useful in tests)</li>
+ *   <li>{@link FileSource} — a single filesystem path</li>
+ *   <li>{@link DirectorySource} — expands a directory into a stream of {@link FileSource}</li>
  *   <li>{@link UriSource} — reads via {@link com.metaobjects.loader.uri.URIHelper}</li>
  * </ul>
  * </p>
  *
  * @see InMemoryStringSource
+ * @see FileSource
+ * @see DirectorySource
  * @see UriSource
  */
 public interface MetaDataSource {