fix(scripts): memoize missing-assembly resolution on the site compile path

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Scripts/ScriptCompilationService.cs

@@ -89,9 +89,21 @@ public class ScriptCompilationService
     /// <c>ScriptAnalysisService.DefaultOptions</c> and
     /// <c>ScriptTrustPolicy.DefaultReferences</c> already follow this pattern.
     /// </para>
+    ///
+    /// <para>
+    /// Static options alone are NOT enough: every <c>script.Compile()</c> binds the
+    /// transitive closure of these references, and Roslyn's default resolver
+    /// re-resolves that closure through <c>MetadataReference.CreateFromFile</c> on
+    /// EVERY compile (~74–105 fresh native metadata copies per compiled script,
+    /// confirmed live post-5a781c70 on 2026-08-12: 21 scripts held 6,640
+    /// AssemblyMetadata/PEReader/MetadataImageReference objects). The shared
+    /// <see cref="CachingScriptMetadataResolver"/> memoizes those resolutions
+    /// process-wide; see its doc for the full mechanism.
+    /// </para>
     /// </summary>
     private static readonly ScriptOptions SharedScriptOptions = ScriptOptions.Default
         .WithReferences(ScriptAssemblies)
+        .WithMetadataResolver(CachingScriptMetadataResolver.Instance)
         .WithImports(
             "System",
             "System.Collections.Generic",

tests/ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests/Scripts/ScriptCompilationServiceTests.cs

@@ -251,4 +251,19 @@ public class ScriptCompilationServiceTests
         // The options object itself is cached, so it must not be rebuilt either.
         Assert.Same(first.CompiledScript.Options, second.CompiledScript.Options);
     }
+
+    [Fact]
+    public void Compile_UsesProcessWideCachingMetadataResolver()
+    {
+        SiteScriptCompileCache.Clear();
+        var result = _service.Compile("resolver-pin", "return 41 + 1;");
+
+        Assert.True(result.IsSuccess);
+        // Without the shared caching resolver, EVERY compile re-resolves the
+        // transitive assembly closure via MetadataReference.CreateFromFile —
+        // ~74+ fresh native metadata copies per compiled script (2026-08-12 dump).
+        Assert.Same(
+            ZB.MOM.WW.ScadaBridge.ScriptAnalysis.CachingScriptMetadataResolver.Instance,
+            result.CompiledScript!.Options.MetadataResolver);
+    }
 }