test(scripts): pin null-result and definition-agnostic caching; review polish

src/ZB.MOM.WW.ScadaBridge.ScriptAnalysis/CachingScriptMetadataResolver.cs

@@ -56,13 +56,25 @@ public sealed class CachingScriptMetadataResolver : MetadataReferenceResolver
 
     private readonly MetadataReferenceResolver _inner;
 
+    // Keyed on the assembly identity display name, compared case-insensitively to
+    // match .NET assembly-name binding, which treats simple names case-insensitively.
+    // A null VALUE is cached too: "not found" is a legitimate, sticky result.
     private readonly ConcurrentDictionary<string, PortableExecutableReference?> _missingByIdentity =
         new(StringComparer.OrdinalIgnoreCase);
 
+    // Deliberately case-SENSITIVE (the tuple's default comparer): baseFilePath is a
+    // filesystem path, and on the Linux containers these nodes run in, two paths
+    // differing only in case are two different files.
     private readonly ConcurrentDictionary<(string Reference, string? BaseFilePath, MetadataReferenceProperties Properties),
-        ImmutableArray<PortableExecutableReference>> _referencesByPath = new();
+        ImmutableArray<PortableExecutableReference>> _referencesByArgs = new();
 
-    /// <summary>Creates a decorator over the given inner resolver. Exposed for tests; production uses <see cref="Instance"/>.</summary>
+    /// <summary>
+    /// Creates a decorator over the given inner resolver. Exposed for tests;
+    /// production code must NEVER call this constructor directly — always attach
+    /// <see cref="Instance"/>. The cache lives on the instance, so a second
+    /// instance has a second (empty) cache and silently reintroduces the
+    /// per-compile native-metadata leak on whichever surface uses it.
+    /// </summary>
     /// <param name="inner">The resolver whose results are memoized.</param>
     public CachingScriptMetadataResolver(MetadataReferenceResolver inner) => _inner = inner;
 
@@ -79,7 +91,7 @@ public sealed class CachingScriptMetadataResolver : MetadataReferenceResolver
     /// <inheritdoc />
     public override ImmutableArray<PortableExecutableReference> ResolveReference(
         string reference, string? baseFilePath, MetadataReferenceProperties properties)
-        => _referencesByPath.GetOrAdd(
+        => _referencesByArgs.GetOrAdd(
             (reference, baseFilePath, properties),
             _ => _inner.ResolveReference(reference, baseFilePath, properties));