fix(build): make format includes portable for CI

 - Add portable format wrapper: fmt::format on macOS, std::format on Linux
 - Add MacPorts clang-18 detection to format.sh and tidy.sh
 - Fix tidy.sh bash portability (mapfile → while read)

 On macOS (where std::format is unavailable), uses fmt library.
 On Linux, creates fmt namespace alias to std::format.

Author: modality

examples/tck_edge_node.cpp

@@ -1,11 +1,18 @@
 #include "tck_edge_node.hpp"
 
 #include <chrono>
-#include <format>
 #include <iostream>
 #include <thread>
 
-#include <fmt/format.h>
+// Portable format: use fmt on macOS (lacks std::format), std::format elsewhere
+#if defined(SPARKPLUG_USE_FMT) || defined(__APPLE__)
+#  include <fmt/format.h>
+#else
+#  include <format>
+namespace fmt {
+using std::format;
+}
+#endif
 
 namespace sparkplug::tck {
 

tests/test_command_handling.cpp

@@ -1,6 +1,16 @@
 // tests/test_command_handling.cpp
 #include <fmt/format.h>
 // Tests for command handling (NCMD/DCMD)
+
+// Portable format: use fmt on macOS (lacks std::format), std::format elsewhere
+#if defined(SPARKPLUG_USE_FMT) || defined(__APPLE__)
+#  include <fmt/format.h>
+#else
+#  include <format>
+namespace fmt {
+using std::format;
+}
+#endif
 #include <atomic>
 #include <cassert>
 #include <iostream>

tests/test_compliance.cpp

@@ -1,6 +1,16 @@
 // tests/test_compliance.cpp
 #include <fmt/format.h>
 // Sparkplug 2.2 Compliance Tests
+
+// Portable format: use fmt on macOS (lacks std::format), std::format elsewhere
+#if defined(SPARKPLUG_USE_FMT) || defined(__APPLE__)
+#  include <fmt/format.h>
+#else
+#  include <format>
+namespace fmt {
+using std::format;
+}
+#endif
 #include <atomic>
 #include <cassert>
 #include <iostream>

tests/test_device_apis.cpp

@@ -1,6 +1,16 @@
 // tests/test_device_apis.cpp
 #include <fmt/format.h>
 // Tests for device-level Sparkplug B APIs (DBIRTH/DDATA/DDEATH)
+
+// Portable format: use fmt on macOS (lacks std::format), std::format elsewhere
+#if defined(SPARKPLUG_USE_FMT) || defined(__APPLE__)
+#  include <fmt/format.h>
+#else
+#  include <format>
+namespace fmt {
+using std::format;
+}
+#endif
 #include <atomic>
 #include <cassert>
 #include <iostream>