Extract JTD test suite from ZIP instead of committing large JSON files (#140)

Previously, two copies of the 78KB jtd-spec-validation.json file were
committed to the repository (156KB total), bloating the PR and git history.

Changes:
- Created JtdTestDataExtractor utility class to extract test data from
  existing jtd-test-suite.zip at test runtime
- Updated JtdSpecConformanceTest and CodegenSpecConformanceTest to use
  extraction instead of classpath resources
- Updated JtdSpecIT and CompilerSpecIT to use shared extractor
- Deleted committed JSON files from both modules
- Codegen module references parent module's ZIP file

Testing:
- Run: ./mvnw -pl json-java21-jtd test
- All 452 tests pass (136 unit + 316 spec conformance)
- Test data is automatically extracted from ZIP on first run
- Reduces PR size by ~156KB (9,390 lines)

Author: simbo1905

json-java21-jtd-codegen/src/test/java/json/java21/jtd/codegen/CodegenSpecConformanceTest.java

@@ -25,18 +25,18 @@
 class CodegenSpecConformanceTest extends CodegenTestBase {
 
   static Stream<Arguments> cases() throws IOException {
-    final var raw = CodegenSpecConformanceTest.class.getClassLoader()
-        .getResourceAsStream("jtd-spec-validation.json");
-    assert raw != null : "jtd-spec-validation.json not found on classpath";
-    final var jsonText = new String(raw.readAllBytes(), StandardCharsets.UTF_8);
-    final var root = Json.parse(jsonText);
-    assert root instanceof JsonObject : "expected top-level object";
-    final var obj = (JsonObject) root;
+    // Extract test suite from ZIP (same data as IT tests, avoids committing large JSON)
+    try (final var raw = JtdTestDataExtractor.getValidationTestDataStream()) {
+      final var jsonText = new String(raw.readAllBytes(), StandardCharsets.UTF_8);
+      final var root = Json.parse(jsonText);
+      assert root instanceof JsonObject : "expected top-level object";
+      final var obj = (JsonObject) root;
 
-    return obj.members().entrySet().stream()
-        .map(entry -> Arguments.of(
-            entry.getKey(),
-            entry.getValue()));
+      return obj.members().entrySet().stream()
+          .map(entry -> Arguments.of(
+              entry.getKey(),
+              entry.getValue()));
+    }
   }
 
   @ParameterizedTest(name = "{0}")

json-java21-jtd-codegen/src/test/java/json/java21/jtd/codegen/JtdTestDataExtractor.java

@@ -0,0 +1,68 @@
+package json.java21.jtd.codegen;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.nio.file.StandardCopyOption;
+import java.util.logging.Logger;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipInputStream;
+
+/// Shared utility for extracting the JTD test suite from the embedded ZIP file.
+/// Used by both unit tests and integration tests to avoid committing large JSON files.
+final class JtdTestDataExtractor {
+  
+  private static final Logger LOG = Logger.getLogger("json.java21.jtd.codegen");
+  // Reference the ZIP file from the sibling json-java21-jtd module
+  private static final Path ZIP_FILE = Paths.get("../json-java21-jtd/src/test/resources/jtd-test-suite.zip");
+  private static final Path TARGET_DIR = Paths.get("target/test-data");
+  private static final Path VALIDATION_FILE = TARGET_DIR.resolve("json-typedef-spec-2025-09-27/tests/validation.json");
+  
+  private JtdTestDataExtractor() {
+    // Utility class
+  }
+  
+  /// Ensures the test suite is extracted and returns the path to validation.json.
+  /// Extraction happens at most once per build (target/ is cleaned between builds).
+  static synchronized Path ensureValidationTestData() throws IOException {
+    if (Files.exists(VALIDATION_FILE)) {
+      LOG.fine(() -> "JTD test suite already extracted at: " + VALIDATION_FILE);
+      return VALIDATION_FILE;
+    }
+    
+    if (!Files.exists(ZIP_FILE)) {
+      throw new RuntimeException("JTD test suite ZIP not found: " + ZIP_FILE.toAbsolutePath());
+    }
+    
+    LOG.info(() -> "Extracting JTD test suite from: " + ZIP_FILE);
+    Files.createDirectories(TARGET_DIR);
+    
+    try (ZipInputStream zis = new ZipInputStream(Files.newInputStream(ZIP_FILE))) {
+      ZipEntry entry;
+      while ((entry = zis.getNextEntry()) != null) {
+        if (!entry.isDirectory() && entry.getName().startsWith("json-typedef-spec-")) {
+          Path outputPath = TARGET_DIR.resolve(entry.getName());
+          Files.createDirectories(outputPath.getParent());
+          Files.copy(zis, outputPath, StandardCopyOption.REPLACE_EXISTING);
+        }
+        zis.closeEntry();
+      }
+    }
+    
+    if (!Files.exists(VALIDATION_FILE)) {
+      throw new RuntimeException("Extraction completed but validation.json not found: " + VALIDATION_FILE);
+    }
+    
+    LOG.info(() -> "JTD test suite extracted successfully");
+    return VALIDATION_FILE;
+  }
+  
+  /// Returns an InputStream for the validation test data, extracting if necessary.
+  /// Suitable for use with classpath-style resource loading patterns.
+  static InputStream getValidationTestDataStream() throws IOException {
+    Path dataFile = ensureValidationTestData();
+    return Files.newInputStream(dataFile);
+  }
+}