chore(java): close H3b-1 caveats — test cross-package extends, retire stale comments, drop orphan fixtures, use type constants

C1: add CanonicalJsonSerializerTest.testExtendsEmittedAsFQNWhenSuperInDifferentPackage and
    testExtendsEmittedAsShortNameWhenSamePackage to cover the FQN/short-name branch in the
    extends emitter (13 tests total, all pass).

C2: strip stale references to JsonMetaDataParser/XMLMetaDataParser from CanonicalJsonParser
    (class Javadoc, JSON_ATTR_PREFIX comment, registry-check comment), MetaDataLoader
    (dispatch comment), and BaseMetaDataParser (import comment + three "moved to" tombstones).

C3: delete seven untracked orphan legacy-envelope JSON fixtures — codegen-base/test-simple.json,
    maven-plugin metaobjects-core.json, core metaobjects-core.json, and four
    test-resources files — all confirmed zero references before deletion.

C4: replace hardcoded "validator"/"view" strings in CanonicalJsonSerializer.isAutoGeneratedName
    with MetaValidator.TYPE_VALIDATOR / MetaView.TYPE_VIEW; add the two imports.

Gate: 385 tests (383 + 2 new), exactly the 8 baseline XSD failures, 0 new failures.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dmealing

java/metadata/src/main/java/com/metaobjects/io/json/CanonicalJsonSerializer.java

@@ -9,6 +9,8 @@
 import com.metaobjects.MetaRoot;
 import com.metaobjects.attr.MetaAttribute;
 import com.metaobjects.field.MetaField;
+import com.metaobjects.validator.MetaValidator;
+import com.metaobjects.view.MetaView;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -414,7 +416,7 @@ private static boolean getNativeIsArray(MetaData node) {
     private static boolean isAutoGeneratedName(MetaData node) {
         String typeName = node.getType();
         // Only validator and view types use auto-naming (mirrors BaseMetaDataParser logic).
-        if (!"validator".equals(typeName) && !"view".equals(typeName)) {
+        if (!MetaValidator.TYPE_VALIDATOR.equals(typeName) && !MetaView.TYPE_VIEW.equals(typeName)) {
             return false;
         }
         String shortName = node.getShortName();

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

@@ -814,9 +814,7 @@ public MetaDataLoader load(List<MetaDataSource> sources) {
                     getName(), LoadingState.Phase.INITIALIZING, 0, e);
             }
 
-            // H3b-1 Task 4: all metadata is canonical JSON; dispatch directly to CanonicalJsonParser.
-            // The legacy XML and natural-JSON parsers still exist in the codebase (deleted in Task 5)
-            // but are no longer used here.
+            // All metadata sources are canonical JSON; dispatch unconditionally to CanonicalJsonParser.
             InputStream is = new ByteArrayInputStream(content.getBytes(StandardCharsets.UTF_8));
             CanonicalJsonParser parser = new CanonicalJsonParser(this, source.getId());
             parser.loadFromStream(is);

java/metadata/src/main/java/com/metaobjects/loader/parser/BaseMetaDataParser.java

@@ -15,7 +15,7 @@
 import com.metaobjects.registry.ChildRequirement;
 import com.metaobjects.relationship.MetaRelationship;
 import com.metaobjects.util.MetaDataUtil;
-// JSON imports moved to JsonMetaDataParser - BaseMetaDataParser should be format-agnostic
+// BaseMetaDataParser is format-agnostic; JSON parsing is handled by CanonicalJsonParser
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -758,8 +758,6 @@ protected void handleNativeIsArrayProperty(MetaData parentMetaData, String strin
         }
     }
 
-    // determineJsonArrayElementType() moved to JsonMetaDataParser
-
     // getAttributeSubTypeFromMetaData() removed - replaced with value-based pattern recognition in determineAttributeSubTypeFromValue()
 
     // getExpectedJavaTypeFromMetaData() removed - replaced with MetaAttribute-first approach
@@ -770,8 +768,6 @@ protected void handleNativeIsArrayProperty(MetaData parentMetaData, String strin
 
     // convertStringToExpectedType() removed - MetaAttribute handles its own value conversion
 
-    // parseJsonStringArray() moved to JsonMetaDataParser
-
     /**
      * Determine appropriate attribute subtype from detected value type (legacy method)
      */
@@ -888,5 +884,4 @@ protected String determineAttributeSubType(String attrName, String stringValue)
     }
 
 
-    // isJsonArray() moved to JsonMetaDataParser
 }

java/metadata/src/main/java/com/metaobjects/loader/parser/json/CanonicalJsonParser.java

@@ -32,8 +32,7 @@
  *   <li><strong>100% registry-driven</strong> — no hardcoded type or subtype names.
  *       New types contributed by a {@code MetaDataTypeProvider} parse without any
  *       edits here.</li>
- *   <li>Behavioural differences from {@link JsonMetaDataParser} are exactly those
- *       mandated by the canonical format:
+ *   <li>Canonical format conventions followed by this reader:
  *       <ol>
  *         <li>Wrapper key is {@code <type>.<subType>} (fused); split on first {@code .}.</li>
  *         <li>Root key is {@code metadata.root}; body has no separate {@code subType} field.</li>
@@ -50,8 +49,7 @@
  *       unchanged.</li>
  * </ul>
  *
- * <p>This class is intentionally a thin layer over {@link BaseMetaDataParser}.
- * {@link JsonMetaDataParser} is untouched; production still uses it until a later task.</p>
+ * <p>This class is intentionally a thin layer over {@link BaseMetaDataParser}.</p>
  */
 public class CanonicalJsonParser extends BaseMetaDataParser implements MetaDataFileParser {
 
@@ -96,10 +94,9 @@ public class CanonicalJsonParser extends BaseMetaDataParser implements MetaDataF
     private static final String TYPE_SUBTYPE_SEPARATOR = ".";
 
     /**
-     * Prefix for inline @-attributes.
-     * Public so that other modules (e.g. codegen-base schema writer) can reference
-     * the canonical attribute-prefix symbol without depending on the deleted
-     * {@code JsonMetaDataParser}.
+     * Prefix for inline @-attributes ({@code "@"}).
+     * Public so that downstream modules (e.g. codegen-base schema writer) can reference
+     * the canonical attribute-prefix constant without depending on this parser's internals.
      */
     public static final String JSON_ATTR_PREFIX = "@";
 
@@ -315,7 +312,7 @@ private void processChildrenArray(MetaData parent, JsonArray children, boolean i
             String type = split.type;
             String subType = split.subType;
 
-            // Registry check — skip unknown types with a warning (mirrors JsonMetaDataParser)
+            // Registry check — skip unknown types with a warning
             if (!getTypeRegistry().hasType(type)) {
                 log.warn("Unknown type '{}' in canonical JSON file [{}] — skipping", type, getFilename());
                 continue;

java/metadata/src/test/java/com/metaobjects/io/json/CanonicalJsonSerializerTest.java

@@ -283,7 +283,65 @@ public void testChildInDifferentPackageEmitsPackageKey() {
     }
 
     // -----------------------------------------------------------------------
-    // Test 11 — validator with authored name ending in digit is NOT suppressed (Fix 1)
+    // Test 11 — extends emitted as FQN when super is in a different package
+    //
+    // Base lives in "other::pkg"; Derived lives in "acme::commerce".
+    // The serializer must emit the fully-qualified "other::pkg::Base" so that
+    // a canonical parser can resolve it without its original load context.
+    // -----------------------------------------------------------------------
+    @Test
+    public void testExtendsEmittedAsFQNWhenSuperInDifferentPackage() {
+        MetaRoot root = new MetaRoot("acme::commerce");
+
+        // Base is in a DIFFERENT package from the root/Derived.
+        MappedMetaObject base = MappedMetaObject.create("other::pkg::Base");
+        base.addMetaAttr(BooleanAttribute.create(MetaData.ATTR_IS_ABSTRACT, true));
+        root.addChild(base);
+
+        MappedMetaObject derived = MappedMetaObject.create("acme::commerce::Derived");
+        derived.setSuperData(base);
+        root.addChild(derived);
+
+        String json = CanonicalJsonSerializer.canonicalSerialize(root);
+
+        // Must use the fully-qualified name because super is in a different package.
+        assertTrue("extends must be the FQN when super is in a different package, got: " + json,
+                json.contains("\"extends\": \"other::pkg::Base\""));
+        // Must NOT use the short name — that would be unresolvable in the canonical parser.
+        assertFalse("extends must NOT be the short name when super is in a different package",
+                json.contains("\"extends\": \"Base\""));
+    }
+
+    // -----------------------------------------------------------------------
+    // Test 12 — extends emitted as short name when super is in the same package
+    //
+    // Both Base and Derived are in "test::pkg".  The existing Test 7 covers
+    // same-package extends; this test makes the intent explicit.
+    // -----------------------------------------------------------------------
+    @Test
+    public void testExtendsEmittedAsShortNameWhenSamePackage() {
+        MetaRoot root = new MetaRoot("test::pkg");
+
+        MappedMetaObject base = MappedMetaObject.create("test::pkg::Base");
+        base.addMetaAttr(BooleanAttribute.create(MetaData.ATTR_IS_ABSTRACT, true));
+        root.addChild(base);
+
+        MappedMetaObject derived = MappedMetaObject.create("test::pkg::Derived");
+        derived.setSuperData(base);
+        root.addChild(derived);
+
+        String json = CanonicalJsonSerializer.canonicalSerialize(root);
+
+        // Same package — short name is unambiguous and preferred.
+        assertTrue("extends must be the short name when super is in the same package, got: " + json,
+                json.contains("\"extends\": \"Base\""));
+        // Must NOT use the FQN — that would be unnecessarily verbose.
+        assertFalse("extends must NOT be the FQN when super is in the same package",
+                json.contains("\"extends\": \"test::pkg::Base\""));
+    }
+
+    // -----------------------------------------------------------------------
+    // Test 13 — validator with authored name ending in digit is NOT suppressed (Fix 1)
     //
     // A RegexValidator named "length2" has subType "regex", so the auto-generated
     // prefix would be "regex". The name "length2" does NOT match "^regex\d+$", so