Add fork safety native methods to TraceExporter

Expose `_native_before_fork`, `_native_after_fork_in_parent`, and
`_native_after_fork_in_child` instance methods that delegate to
libdatadog's SharedRuntime fork hooks. These coordinate the tokio
runtime lifecycle around process forks (Puma, Unicorn, Passenger).

Author: lloeki

ext/libdatadog_api/trace_exporter.c

@@ -20,6 +20,9 @@ static VALUE _native_from_span(VALUE klass, VALUE span);
 /* TraceExporter methods */
 static VALUE _native_exporter_new(int argc, VALUE *argv, VALUE klass);
 static VALUE _native_send_traces(VALUE self, VALUE traces);
+static VALUE _native_before_fork(VALUE self);
+static VALUE _native_after_fork_in_parent(VALUE self);
+static VALUE _native_after_fork_in_child(VALUE self);
 
 /* Response helpers */
 static VALUE create_ok_response(long trace_count, VALUE payload);
@@ -473,6 +476,46 @@ static VALUE _native_exporter_new(
                                exporter);
 }
 
+/* ========================================================================
+ * Fork safety hooks
+ *
+ * These coordinate the tokio runtime lifecycle around process forks
+ * (Puma, Unicorn, Passenger).
+ * ======================================================================== */
+
+static VALUE _native_before_fork(VALUE self) {
+  ddog_TraceExporter *exporter;
+  TypedData_Get_Struct(self, ddog_TraceExporter, &trace_exporter_typed_data, exporter);
+  if (exporter == NULL) {
+    raise_error(rb_eRuntimeError, "TraceExporter has not been initialized or was already freed");
+  }
+  ddog_TraceExporterError *err = ddog_trace_exporter_before_fork(exporter);
+  check_exporter_error("Failed to prepare for fork", err);
+  return Qnil;
+}
+
+static VALUE _native_after_fork_in_parent(VALUE self) {
+  ddog_TraceExporter *exporter;
+  TypedData_Get_Struct(self, ddog_TraceExporter, &trace_exporter_typed_data, exporter);
+  if (exporter == NULL) {
+    raise_error(rb_eRuntimeError, "TraceExporter has not been initialized or was already freed");
+  }
+  ddog_TraceExporterError *err = ddog_trace_exporter_after_fork_in_parent(exporter);
+  check_exporter_error("Failed to restore after fork in parent", err);
+  return Qnil;
+}
+
+static VALUE _native_after_fork_in_child(VALUE self) {
+  ddog_TraceExporter *exporter;
+  TypedData_Get_Struct(self, ddog_TraceExporter, &trace_exporter_typed_data, exporter);
+  if (exporter == NULL) {
+    raise_error(rb_eRuntimeError, "TraceExporter has not been initialized or was already freed");
+  }
+  ddog_TraceExporterError *err = ddog_trace_exporter_after_fork_in_child(exporter);
+  check_exporter_error("Failed to restore after fork in child", err);
+  return Qnil;
+}
+
 /* ========================================================================
  * GVL-release helper for ddog_trace_exporter_send_trace_chunks
  *
@@ -736,6 +779,14 @@ void trace_exporter_init(VALUE tracing_module) {
   rb_define_method(trace_exporter_class, "_native_send_traces",
                    _native_send_traces, 1);
 
+  /* Instance: fork safety hooks */
+  rb_define_method(trace_exporter_class, "_native_before_fork",
+                   _native_before_fork, 0);
+  rb_define_method(trace_exporter_class, "_native_after_fork_in_parent",
+                   _native_after_fork_in_parent, 0);
+  rb_define_method(trace_exporter_class, "_native_after_fork_in_child",
+                   _native_after_fork_in_child, 0);
+
   /* ----------------------------------------------------------------
    * Response class (defined in Ruby, loaded lazily)
    *