chore(example): demonstrate __codspeed_root_frame__ pattern

Wraps the benchmarked call in a noinline __codspeed_root_frame__ helper
so the example matches the pattern documented in the custom harness
guide.

Author: not-matthias

example/main.c

@@ -22,9 +22,12 @@ void example_function() {
   printf("Benchmark executed\n");
 }
 
-int main() {
-  instrument_hooks_set_feature(FEATURE_DISABLE_CALLGRIND_MARKERS, true);
+__attribute__((noinline)) void __codspeed_root_frame__example(
+    void (*benchmark_fn)(void)) {
+  benchmark_fn();
+}
 
+int main() {
   InstrumentHooks *hooks = instrument_hooks_init();
   if (!hooks) {
     printf("Failed to initialize instrument hooks\n");
@@ -37,7 +40,7 @@ int main() {
     printf("Not running under instrumentation\n");
   }
 
-  instrument_hooks_set_integration(hooks, "example", "1.0.0");
+  instrument_hooks_set_integration(hooks, "custom-integration", "1.0.0");
 
   printf("Starting benchmark...\n");
   if (instrument_hooks_start_benchmark_inline(hooks) != 0) {
@@ -53,7 +56,7 @@ int main() {
     expensive_setup();
 
     uint64_t start_time = instrument_hooks_current_timestamp();
-    example_function();
+    __codspeed_root_frame__example(example_function);
     uint64_t end_time = instrument_hooks_current_timestamp();
 
     // Add the markers which mark when the benchmarked function was running