Add _beginSection and _endSection JSI bindings for systraces (#9101)

## Summary

This PR adds `_beginSection` and `_endSection` JSI bindings in worklet
runtimes (e.g. Reanimated UI runtime) that begin and end systrace
sections, respectively, both on Android and iOS.

Usage:
```tsx
scheduleOnUI(() => {
  globalThis._beginSection('systrace name here');
  // your code here
  globalThis._endSection();
});
```

Android Profiler:
<img width="1121" height="280" alt="Screenshot 2026-03-13 at 23 45 37"
src="https://github.com/user-attachments/assets/7306b694-553b-4340-a787-9e61bd200159"
/>

Xcode instruments:
<img width="1177" height="333" alt="Screenshot 2026-03-13 at 23 46 51"
src="https://github.com/user-attachments/assets/020a2048-3693-457a-9bec-1d12342cea63"
/>

For profiling the RN runtime you can use `Systrace` from `react-native`
([docs](https://reactnative.dev/docs/systrace)).

## Test plan

Author: tomekzaw

apps/common-app/src/apps/reanimated/examples/SystraceSectionExample.tsx

@@ -0,0 +1,39 @@
+import { Button, StyleSheet, Text, View } from 'react-native';
+
+import React from 'react';
+import { scheduleOnUI } from 'react-native-worklets';
+
+declare global {
+  var _beginSection: (name: string) => void;
+  var _endSection: () => void;
+}
+
+function handlePress() {
+  scheduleOnUI(() => {
+    globalThis._beginSection('SystraceSectionExample');
+    const start = performance.now();
+    // eslint-disable-next-line no-empty
+    while (performance.now() - start < 1000) {}
+    globalThis._endSection();
+  });
+}
+
+export default function SystraceSectionExample() {
+  return (
+    <View style={styles.container}>
+      <Text>Hello world!</Text>
+      <Button
+        title="Begin section, wait 1 second, end section"
+        onPress={handlePress}
+      />
+    </View>
+  );
+}
+
+const styles = StyleSheet.create({
+  container: {
+    flex: 1,
+    alignItems: 'center',
+    justifyContent: 'center',
+  },
+});

apps/common-app/src/apps/reanimated/examples/index.ts

@@ -144,6 +144,7 @@ import SvgExample from './SvgExample';
 import SwipeableListExample from './SwipeableListExample';
 import SynchronizablePerformanceExample from './SynchronizableExample';
 import SynchronousPropsExample from './SynchronousPropsExample';
+import SystraceSectionExample from './SystraceSectionExample';
 import ThirdPartyComponentsExample from './ThirdPartyComponentsExample';
 import TransformExample from './TransformExample';
 import TransformOriginExample from './TransformOriginExample';
@@ -198,6 +199,11 @@ export const EXAMPLES: Record<string, Example> = {
     title: 'FPS',
     screen: FpsExample,
   },
+  SystraceSectionExample: {
+    icon: '📊',
+    title: 'Systrace section',
+    screen: SystraceSectionExample,
+  },
   SyncBackToReactExample: {
     icon: '🔄',
     title: 'Sync back to React',

packages/react-native-reanimated/src/privateGlobals.d.ts

@@ -24,6 +24,8 @@ declare global {
   var _REANIMATED_VERSION_JS: string | undefined;
   var __reanimatedModuleProxy: ReanimatedModuleProxy | undefined;
   var _log: (value: unknown) => void;
+  var _beginSection: (name: string) => void;
+  var _endSection: () => void;
   var _notifyAboutProgress: (
     tag: number,
     value: Record<string, unknown>

packages/react-native-worklets/Common/cpp/worklets/WorkletRuntime/WorkletRuntimeDecorator.cpp

@@ -7,11 +7,36 @@
 #include <worklets/WorkletRuntime/WorkletRuntime.h>
 #include <worklets/WorkletRuntime/WorkletRuntimeDecorator.h>
 
+#ifdef ANDROID
+#include <android/trace.h>
+#endif
+
+#if defined(__APPLE__)
+#include <os/trace_base.h>
+#if OS_LOG_TARGET_HAS_10_15_FEATURES
+#include <os/log.h>
+#include <os/signpost.h>
+#endif
+#endif
+
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
+#if defined(__APPLE__) && OS_LOG_TARGET_HAS_10_15_FEATURES
+static os_log_t workletsInstrumentsLogHandle = nullptr;
+static thread_local os_signpost_id_t tls_signpostId = OS_SIGNPOST_ID_INVALID;
+static thread_local std::string tls_signpostName;
+
+static os_log_t getWorkletsInstrumentsLogHandle() {
+  if (!workletsInstrumentsLogHandle) {
+    workletsInstrumentsLogHandle = os_log_create("dev.worklets.instruments", OS_LOG_CATEGORY_POINTS_OF_INTEREST);
+  }
+  return workletsInstrumentsLogHandle;
+}
+#endif
+
 namespace worklets {
 
 static inline double performanceNow() {
@@ -87,6 +112,33 @@ void WorkletRuntimeDecorator::decorate(
     return jsi::String::createFromUtf8(rt, stringifyJSIValue(rt, value));
   });
 
+  jsi_utils::installJsiFunction(rt, "_beginSection", [](jsi::Runtime &rt, const jsi::Value &nameValue) {
+#ifdef ANDROID
+    ATrace_beginSection(nameValue.asString(rt).utf8(rt).c_str());
+#elif defined(__APPLE__) && OS_LOG_TARGET_HAS_10_15_FEATURES
+    os_log_t logHandle = getWorkletsInstrumentsLogHandle();
+    if (os_signpost_enabled(logHandle)) {
+      tls_signpostName = nameValue.asString(rt).utf8(rt);
+      tls_signpostId = os_signpost_id_make_with_pointer(logHandle, &tls_signpostId);
+      os_signpost_interval_begin(logHandle, tls_signpostId, "Worklets", "%s", tls_signpostName.c_str());
+    }
+#endif
+    return jsi::Value::undefined();
+  });
+
+  jsi_utils::installJsiFunction(rt, "_endSection", [](jsi::Runtime &rt) {
+#ifdef ANDROID
+    ATrace_endSection();
+#elif defined(__APPLE__) && OS_LOG_TARGET_HAS_10_15_FEATURES
+    os_log_t logHandle = getWorkletsInstrumentsLogHandle();
+    if (os_signpost_enabled(logHandle) && tls_signpostId != OS_SIGNPOST_ID_INVALID) {
+      os_signpost_interval_end(logHandle, tls_signpostId, "Worklets", "%s end", tls_signpostName.c_str());
+      tls_signpostId = OS_SIGNPOST_ID_INVALID;
+    }
+#endif
+    return jsi::Value::undefined();
+  });
+
   jsi_utils::installJsiFunction(
       rt, "_createSerializable", [](jsi::Runtime &rt, const jsi::Value &value, const jsi::Value &nativeStateSource) {
         auto shouldRetainRemote = jsi::Value::undefined();

packages/react-native-worklets/android/CMakeLists.txt

@@ -96,7 +96,7 @@ target_include_directories(
 # build shared lib
 set_target_properties(worklets PROPERTIES LINKER_LANGUAGE CXX)
 
-target_link_libraries(worklets log ReactAndroid::reactnative ReactAndroid::jsi
+target_link_libraries(worklets android log ReactAndroid::reactnative ReactAndroid::jsi
                       fbjni::fbjni)
 
 if(${JS_RUNTIME} STREQUAL "hermes")

packages/react-native-worklets/src/privateGlobals.d.ts

@@ -73,6 +73,8 @@ declare global {
   var __flushAnimationFrame: (timestamp: number) => void;
   var __frameTimestamp: number | undefined;
   var _log: (value: unknown) => void;
+  var _beginSection: (name: string) => void;
+  var _endSection: () => void;
   var _getAnimationTimestamp: () => number;
   var _scheduleOnRuntime: (
     runtime: WorkletRuntime,