merge: C# ADR-0003/0004 colocation + @schema/@storage parity

Brings worktree-csharp-parity-plans onto main:
- ADR-0003 constants/schemas colocated per concern; god-files deleted; @javaruntime leak removed
- ADR-0004 provider model marked shipped for C#
- @Schema constants; @storage first-class (enum schema + cross-attr validator + 4 tests)
Conformance 174/0.

Author: dmealing

server/csharp/MetaObjects.Conformance.Tests/GlobalUsings.cs

@@ -0,0 +1,17 @@
+// Metamodel-constants barrel for the conformance test assembly (ADR-0003 §3).
+// Mirrors MetaObjects/GlobalUsings.cs so tests reference colocated constants as bare names.
+
+global using static MetaObjects.Shared.BaseTypes;
+global using static MetaObjects.Shared.Structural;
+global using static MetaObjects.Core.Attr.AttrConstants;
+global using static MetaObjects.Core.Query.QueryConstants;
+global using static MetaObjects.Core.Field.FieldConstants;
+global using static MetaObjects.Core.Object.ObjectConstants;
+global using static MetaObjects.Core.Validator.ValidatorConstants;
+global using static MetaObjects.Core.Identity.IdentityConstants;
+global using static MetaObjects.Core.Relationship.RelationshipConstants;
+global using static MetaObjects.Persistence.Source.SourceConstants;
+global using static MetaObjects.Persistence.Origin.OriginConstants;
+global using static MetaObjects.Persistence.Db.DbConstants;
+global using static MetaObjects.Presentation.View.ViewConstants;
+global using static MetaObjects.Presentation.Layout.LayoutConstants;

server/csharp/MetaObjects.Conformance.Tests/Loader/FieldObjectStorageValidationTests.cs

@@ -0,0 +1,137 @@
+using System.Collections.Generic;
+using System.Linq;
+using MetaObjects;
+using MetaObjects.Loader;
+using Xunit;
+
+namespace MetaObjects.Conformance.Tests.Loader;
+
+/// <summary>
+/// Cross-attribute validation for @storage on field.object. Mirrors the TS
+/// storage-validation tests (validateFieldObjectStorage in validation-passes.ts):
+///   - @storage requires @objectRef on the same field.
+///   - @storage "flattened" requires isArray=false.
+/// </summary>
+public class FieldObjectStorageValidationTests
+{
+    private static (bool ok, IReadOnlyList<ErrorCode> codes) Load(string json)
+    {
+        var result = new MetaDataLoader().Load([new InMemorySource(json, id: "storage.json")]);
+        return (result.Errors.Count == 0, result.Errors.Select(e => e.Code).ToList());
+    }
+
+    [Fact]
+    public void Storage_without_objectRef_is_rejected()
+    {
+        var (ok, codes) = Load("""
+        {
+          "metadata.root": {
+            "package": "test",
+            "children": [
+              {
+                "object.entity": {
+                  "name": "Order",
+                  "children": [
+                    { "source.dbTable": { "@name": "orders" } },
+                    { "field.object": { "name": "addr", "@storage": "flattened" } },
+                    { "field.long":   { "name": "id" } },
+                    { "identity.primary": { "@fields": "id" } }
+                  ]
+                }
+              }
+            ]
+          }
+        }
+        """);
+        Assert.False(ok);
+        Assert.Contains(ErrorCode.ERR_STORAGE_WITHOUT_OBJECT_REF, codes);
+    }
+
+    [Fact]
+    public void Storage_flattened_with_isArray_true_is_rejected()
+    {
+        var (ok, codes) = Load("""
+        {
+          "metadata.root": {
+            "package": "test",
+            "children": [
+              { "object.value": { "name": "Address", "children": [
+                { "field.string": { "name": "street" } }
+              ]}},
+              {
+                "object.entity": {
+                  "name": "Order",
+                  "children": [
+                    { "source.dbTable": { "@name": "orders" } },
+                    { "field.object": { "name": "addrs", "isArray": true, "@objectRef": "Address", "@storage": "flattened" } },
+                    { "field.long":   { "name": "id" } },
+                    { "identity.primary": { "@fields": "id" } }
+                  ]
+                }
+              }
+            ]
+          }
+        }
+        """);
+        Assert.False(ok);
+        Assert.Contains(ErrorCode.ERR_STORAGE_FLATTENED_ARRAY, codes);
+    }
+
+    [Fact]
+    public void Storage_flattened_with_objectRef_and_isArray_false_passes()
+    {
+        var (ok, codes) = Load("""
+        {
+          "metadata.root": {
+            "package": "test",
+            "children": [
+              { "object.value": { "name": "Address", "children": [
+                { "field.string": { "name": "street" } }
+              ]}},
+              {
+                "object.entity": {
+                  "name": "Order",
+                  "children": [
+                    { "source.dbTable": { "@name": "orders" } },
+                    { "field.object": { "name": "addr", "@objectRef": "Address", "@storage": "flattened" } },
+                    { "field.long":   { "name": "id" } },
+                    { "identity.primary": { "@fields": "id" } }
+                  ]
+                }
+              }
+            ]
+          }
+        }
+        """);
+        Assert.True(ok, $"expected no errors, got: {string.Join(", ", codes)}");
+    }
+
+    [Fact]
+    public void Storage_jsonb_with_isArray_true_passes()
+    {
+        var (ok, codes) = Load("""
+        {
+          "metadata.root": {
+            "package": "test",
+            "children": [
+              { "object.value": { "name": "ContactInfo", "children": [
+                { "field.string": { "name": "email" } }
+              ]}},
+              {
+                "object.entity": {
+                  "name": "Patient",
+                  "children": [
+                    { "source.dbTable": { "@name": "patients" } },
+                    { "field.object": { "name": "contactInfos", "isArray": true, "@objectRef": "ContactInfo", "@storage": "jsonb" } },
+                    { "field.long":   { "name": "id" } },
+                    { "identity.primary": { "@fields": "id" } }
+                  ]
+                }
+              }
+            ]
+          }
+        }
+        """);
+        Assert.True(ok, $"expected no errors, got: {string.Join(", ", codes)}");
+    }
+}