fix(codegen-csharp): FR-021 TryResolve — apply PackageNamespaces to @provided enums

TryResolve carried a `!useProvidedEnumPrepend` guard that skipped the
package-level override (PackageNamespaces) for @provided enums, leaving the
helper inconsistent with ResolveImpl (whose step 2 is unguarded) and with
SharedEnumTypeReference's own documented order (TypeOverrides → PackageNamespaces
→ Convention → ProvidedEnumNamespace). A provided enum has its own declaring
package, distinct from any entity package, so an explicit PackageNamespaces entry
for it is a deliberate binding that must win (the FR-019 "namespace maps to the
declaring package" contract). Parallel-tree routing stays expressed via
Convention.ProvidedEnumPrepend, not by suppressing the explicit override.

Greens the 3 reds in the FR-021 WIP (its own TryResolve-returns-null test, which
asserts "package-level override always wins even for provided enums", plus the
two FR-019 package-binding tests). No test changes — the tests were correct.

Codegen 205/0, Conformance 592/0, solution builds clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: dmealing

server/csharp/MetaObjects.Codegen/PackageBindingResolver.cs

@@ -119,12 +119,14 @@ public static string ResolveForProvidedEnum(
             if (config.TypeOverrides.TryGetValue(fqn, out var typeTarget) && !string.IsNullOrEmpty(typeTarget))
                 return typeTarget;
         }
-        // 2. Package-level override — applies ONLY to the default resolution path.
-        //    @provided enums often live in a parallel namespace tree from entities; a
-        //    PackageNamespaces override (which targets entity placement) must not bleed
-        //    into the @provided enum case.
-        if (!useProvidedEnumPrepend &&
-            !string.IsNullOrEmpty(package) &&
+        // 2. Package-level override — keyed by the metadata package, so it applies to BOTH
+        //    paths: a provided enum has its OWN declaring package (distinct from any entity
+        //    package), and an explicit PackageNamespaces entry for that package is a
+        //    deliberate binding that must win (matching ResolveImpl's unguarded step 2 and
+        //    the FR-019 "namespace maps to the declaring package" contract). Parallel-tree
+        //    routing for provided enums is expressed via Convention.ProvidedEnumPrepend
+        //    (step 3), not by suppressing this explicit override.
+        if (!string.IsNullOrEmpty(package) &&
             config.PackageNamespaces.TryGetValue(package, out var pkgTarget) &&
             !string.IsNullOrEmpty(pkgTarget))
         {