refactor(java): post-review simplifications in Stage 2 Unit 1

- ValidationPhase: replace manual MetaSource child iteration in
  validateObjectPrimarySource with obj.getSources() (own-only)
- ValidationPhase: replace 5-way &&-chain @kind check with
  MetaSource.VALID_KINDS.contains(), matching REFERENTIAL_ACTIONS pattern
- ValidationPhase: replace 6-way &&-chain @ROLE check with
  MetaSource.VALID_ROLES.contains()
- MetaSource: add VALID_KINDS and VALID_ROLES Set constants, symmetric
  to the existing READ_ONLY_KINDS and the relationship REFERENTIAL_ACTIONS

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: dmealing

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

@@ -204,11 +204,7 @@ private static void validateSourceNode(MetaData node) {
         // Validate @kind (own attribute only — defaults are fine)
         if (node.hasMetaAttr(MetaSource.ATTR_KIND, false)) {
             String kind = src.getEffectiveKind();
-            if (!MetaSource.KIND_TABLE.equals(kind)
-                    && !MetaSource.KIND_VIEW.equals(kind)
-                    && !MetaSource.KIND_MATERIALIZED_VIEW.equals(kind)
-                    && !MetaSource.KIND_STORED_PROC.equals(kind)
-                    && !MetaSource.KIND_TABLE_FUNCTION.equals(kind)) {
+            if (!MetaSource.VALID_KINDS.contains(kind)) {
                 throw new MetaDataException(
                     ErrorMessageConstants.ERR_BAD_ATTR_VALUE
                         + ": source '" + node.getName()
@@ -222,12 +218,7 @@ private static void validateSourceNode(MetaData node) {
         // Validate @role (own attribute only — defaults are fine)
         if (node.hasMetaAttr(MetaSource.ATTR_ROLE, false)) {
             String role = src.getRole();
-            if (!MetaSource.ROLE_PRIMARY.equals(role)
-                    && !MetaSource.ROLE_REPLICA.equals(role)
-                    && !MetaSource.ROLE_INDEX.equals(role)
-                    && !MetaSource.ROLE_CACHE.equals(role)
-                    && !MetaSource.ROLE_PUBLISH.equals(role)
-                    && !MetaSource.ROLE_MIRROR.equals(role)) {
+            if (!MetaSource.VALID_ROLES.contains(role)) {
                 throw new MetaDataException(
                     ErrorMessageConstants.ERR_BAD_ATTR_VALUE
                         + ": source '" + node.getName()
@@ -287,13 +278,9 @@ private static void walkOnePrimarySource(MetaData node) {
      * @throws MetaDataException if the one-primary rule is violated
      */
     private static void validateObjectPrimarySource(MetaObject obj) {
-        // Collect own MetaSource children (own-only, includeParentData=false).
-        java.util.List<MetaSource> sources = new java.util.ArrayList<>();
-        for (MetaData child : obj.getChildren(MetaData.class, false)) {
-            if (child instanceof MetaSource) {
-                sources.add((MetaSource) child);
-            }
-        }
+        // Own-only MetaSource children — delegates to MetaObject.getSources() to avoid
+        // duplicating the child-collection logic here.
+        java.util.Collection<MetaSource> sources = obj.getSources();
 
         if (sources.isEmpty()) {
             // No sources declared — object is not persisted; no rule to enforce.

server/java/metadata/src/main/java/com/metaobjects/source/MetaSource.java

@@ -64,6 +64,15 @@ public abstract class MetaSource extends MetaData {
         KIND_TABLE_FUNCTION
     );
 
+    /** All valid {@code @kind} values. Used by {@code ValidationPhase} for enum-membership checks. */
+    public static final Set<String> VALID_KINDS = Set.of(
+        KIND_TABLE,
+        KIND_VIEW,
+        KIND_MATERIALIZED_VIEW,
+        KIND_STORED_PROC,
+        KIND_TABLE_FUNCTION
+    );
+
     // === ROLE VALUE CONSTANTS ===
 
     public static final String ROLE_PRIMARY = "primary";
@@ -76,6 +85,11 @@ public abstract class MetaSource extends MetaData {
     /** Default role when {@code @role} is absent. */
     public static final String DEFAULT_ROLE = ROLE_PRIMARY;
 
+    /** All valid {@code @role} values. Used by {@code ValidationPhase} for enum-membership checks. */
+    public static final Set<String> VALID_ROLES = Set.of(
+        ROLE_PRIMARY, ROLE_REPLICA, ROLE_INDEX, ROLE_CACHE, ROLE_PUBLISH, ROLE_MIRROR
+    );
+
     // -----------------------------------------------------------------------
     // Constructor
     // -----------------------------------------------------------------------