chore(mocks): tighten EscapeIdentifier visibility, document GetWrappe…

…rName decision

Round-2 review feedback on #5679:
- IdentifierEscaping.EscapeIdentifier is now `internal` (was misleadingly
  `public` inside an internal class).
- Added a one-line WHY comment above MockMembersBuilder.GetWrapperName
  explaining that embedding the raw method name into the compound
  wrapper identifier is intentional — a keyword as a non-terminal
  substring is valid C#, so EscapeIdentifier is not needed there.

TUnit.Mocks.SourceGenerator/Builders/MockMembersBuilder.cs

@@ -134,6 +134,11 @@ private static bool ShouldGenerateTypedWrapper(MockMemberModel method, bool hasE
         return matchableParams.Count <= MaxTypedParams;
     }
 
+    // method.Name is intentionally embedded raw (unescaped) here. The result is a compound
+    // identifier like "IFoo_event_M2_MockCall" — even when method.Name is a C# keyword such as
+    // "event" or "class", it appears only as a non-terminal substring of a larger token, which is
+    // a valid C# identifier. Escaping (via EscapeIdentifier) is only required when the name would
+    // stand alone as a complete identifier in the emitted source.
     private static string GetWrapperName(string safeName, MockMemberModel method)
         => $"{safeName}_{method.Name}_M{method.MemberId}_MockCall";
 

TUnit.Mocks.SourceGenerator/IdentifierEscaping.cs

@@ -24,6 +24,6 @@ internal static class IdentifierEscaping
     // C# compiler already disambiguates them by position. Escaping a contextual keyword would
     // change the identifier's textual form (e.g. `record` → `@record`), breaking explicit
     // interface implementation matching against the source-declared member name.
-    public static string EscapeIdentifier(string name) =>
+    internal static string EscapeIdentifier(string name) =>
         SyntaxFacts.GetKeywordKind(name) != SyntaxKind.None ? "@" + name : name;
 }