perf: cache CreateExecutableTestFactory delegate (#4292)

* chore: add .worktrees/ to gitignore

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* perf: cache CreateExecutableTestFactory delegate

Cache the factory delegate instead of creating new lambdas on every
property access. This avoids repeated allocations in the hot path
during test execution.

Fixes #4281

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: thomhurst

.gitignore

@@ -435,4 +435,7 @@ doc/plans/
 *speedscope*.json
 
 # Dotnet trace files
-*.nettrace
+*.nettrace
+
+# Git worktrees
+.worktrees/

TUnit.Core/TestMetadata`1.cs

@@ -14,6 +14,7 @@ public class TestMetadata<
 {
     private Func<Type[], object?[], T>? _instanceFactory;
     private Func<T, object?[], Task>? _testInvoker;
+    private Func<ExecutableTestCreationContext, TestMetadata, AbstractExecutableTest>? _cachedExecutableTestFactory;
 
     /// <summary>
     /// Strongly typed instance factory
@@ -63,10 +64,16 @@ public override Func<ExecutableTestCreationContext, TestMetadata, AbstractExecut
     {
         get
         {
+            // Return cached factory if available
+            if (_cachedExecutableTestFactory != null)
+            {
+                return _cachedExecutableTestFactory;
+            }
+
             // For AOT mode, create delegates from the strongly-typed ones
             if (InstanceFactory != null && InvokeTypedTest != null)
             {
-                return (context, metadata) =>
+                _cachedExecutableTestFactory = (context, metadata) =>
                 {
                     var typedMetadata = (TestMetadata<T>)metadata;
 
@@ -109,6 +116,8 @@ public override Func<ExecutableTestCreationContext, TestMetadata, AbstractExecut
                         Context = context.Context
                     };
                 };
+
+                return _cachedExecutableTestFactory;
             }
 
             throw new InvalidOperationException($"InstanceFactory and InvokeTypedTest must be set for {typeof(T).Name}");