Rename ArenaAllocator -> Arena

tests/test_metric.cpp

@@ -1,6 +1,6 @@
 #include <doctest/doctest.h>
 
-#include "arena_allocator.hpp"
+#include "arena.hpp"
 #include "metric.hpp"
 
 #include <atomic>
@@ -279,7 +279,7 @@ TEST_CASE("callback-based metrics") {
                                      []() { return 42.0; });
 
     // Callback should be called during render
-    ArenaAllocator arena;
+    Arena arena;
     auto output = metric::render(arena);
     CHECK(output.size() > 0);
   }
@@ -288,7 +288,7 @@ TEST_CASE("callback-based metrics") {
     gauge_family.register_callback({{"type", "callback"}},
                                    []() { return 123.5; });
 
-    ArenaAllocator arena;
+    Arena arena;
     auto output = metric::render(arena);
     CHECK(output.size() > 0);
   }
@@ -304,7 +304,7 @@ TEST_CASE("callback-based metrics") {
 }
 
 TEST_CASE("prometheus text format rendering") {
-  ArenaAllocator arena;
+  Arena arena;
 
   // Create some metrics
   auto counter_family =
@@ -463,7 +463,7 @@ TEST_CASE("thread safety") {
       threads.emplace_back([&]() {
         start_latch.arrive_and_wait();
 
-        ArenaAllocator arena;
+        Arena arena;
         auto output = metric::render(arena);
         if (output.size() > 0) {
           success_count.fetch_add(1);
@@ -503,7 +503,7 @@ TEST_CASE("thread counter cleanup bug") {
 
       // Measure actual values from within the thread (before ThreadInit
       // destructor runs)
-      ArenaAllocator thread_arena;
+      Arena thread_arena;
       auto thread_output = metric::render(thread_arena);
 
       for (const auto &line : thread_output) {
@@ -538,7 +538,7 @@ TEST_CASE("thread counter cleanup bug") {
     worker.join();
 
     // Measure values after thread cleanup
-    ArenaAllocator arena;
+    Arena arena;
     auto output = metric::render(arena);
 
     double counter_value_after = 0;
@@ -615,7 +615,7 @@ TEST_CASE("error conditions") {
 
 TEST_CASE("memory management") {
   SUBCASE("arena allocation in render") {
-    ArenaAllocator arena;
+    Arena arena;
     auto initial_used = arena.used_bytes();
 
     auto counter_family = metric::create_counter("memory_test", "Memory test");
@@ -636,7 +636,7 @@ TEST_CASE("memory management") {
   }
 
   SUBCASE("arena reset behavior") {
-    ArenaAllocator arena;
+    Arena arena;
 
     auto counter_family = metric::create_counter("reset_test", "Reset test");
     auto counter = counter_family.create({});
@@ -659,7 +659,7 @@ TEST_CASE("render output deterministic order golden test") {
   // Clean slate - reset all metrics before this test
   metric::reset_metrics_for_testing();
 
-  ArenaAllocator arena;
+  Arena arena;
 
   // Create a comprehensive set of metrics with deliberate ordering
   // to test deterministic output