Simplify StrCat specialization: remove if constexpr branch

All N values (including N==2) now use _MakeStringWithSpace to create a
combined string+space buffer and perform a single append call. This is
cleaner and avoids the two-operation path for single-char literals too.

Agent-Logs-Url: https://github.com/Cpp2Rust/cpp2rust/sessions/3ee80ab3-b415-4172-90d7-3a80ee9aa747

Co-authored-by: nunoplopes <2998477+nunoplopes@users.noreply.github.com>

Author: Copilot

cpp2rust/converter/converter.h

@@ -336,21 +336,15 @@ class Converter : public clang::RecursiveASTVisitor<Converter> {
     rs_code += ' ';
   }
 
-  // Specialization for string literals (const char[N]):
-  //  - N == 2 (single char, e.g. "("): use character append rather than string
-  //    append to avoid a strlen scan.
-  //  - N > 2 (longer string): combine the string and trailing space into one
-  //    contiguous buffer and append it in a single call.
+  // Specialization for string literals (const char[N]): combines the string
+  // content and a trailing space into a single contiguous buffer (using the
+  // compile-time size N to skip any strlen scan) and appends it in one call.
+  // This covers all lengths, including single-char literals such as "(".
   template <std::size_t N>
   static void AppendToCode(std::string &rs_code, const char (&val)[N]) {
-    if constexpr (N == 2) {
-      rs_code += val[0];
-      rs_code += ' ';
-    } else {
-      const auto combined =
-          _MakeStringWithSpace(val, std::make_index_sequence<N - 1>{});
-      rs_code.append(combined.data(), N);
-    }
+    const auto combined =
+        _MakeStringWithSpace(val, std::make_index_sequence<N - 1>{});
+    rs_code.append(combined.data(), N);
   }
 
   class Buffer {