Add ThreadContext.put(spanId, traceIdHigh, traceIdLow) for 128-bit trace IDs

Routes to ContextApi::setOtel() via new setContextOtel0 JNI method,
enabling tracers to set full W3C 128-bit trace IDs.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Author: jbachorik

ddprof-lib/src/main/cpp/javaApi.cpp

@@ -572,6 +572,11 @@ Java_com_datadoghq_profiler_ThreadContext_setContext0(JNIEnv* env, jclass unused
   return Contexts::checksum(spanId, rootSpanId);
 }
 
+extern "C" DLLEXPORT void JNICALL
+Java_com_datadoghq_profiler_ThreadContext_setContextOtel0(JNIEnv* env, jclass unused, jlong traceIdHigh, jlong traceIdLow, jlong spanId) {
+  ContextApi::setOtel(traceIdHigh, traceIdLow, spanId);
+}
+
 // Legacy API: writes directly to Context.tags[] regardless of storage mode.
 // In OTEL mode, writeCurrentContext() in flightRecorder.cpp reads both Context.tags[]
 // and the OTEP attrs_data, so tags set via this path are still recorded in JFR.

ddprof-lib/src/main/java/com/datadoghq/profiler/ThreadContext.java

@@ -161,6 +161,19 @@ public long put(long spanId, long rootSpanId) {
         return (useJNI || otelMode) ? setContext0(spanId, rootSpanId) : putContextJava(spanId, rootSpanId);
     }
 
+    /**
+     * Sets trace context with full 128-bit W3C trace ID support.
+     * In OTEL mode, all three values are written to the OTEP record.
+     * In profiler mode, traceIdHigh is ignored (Datadog uses 64-bit trace IDs).
+     *
+     * @param spanId The span ID
+     * @param traceIdHigh Upper 64 bits of the 128-bit trace ID
+     * @param traceIdLow Lower 64 bits of the 128-bit trace ID (rootSpanId in Datadog)
+     */
+    public void put(long spanId, long traceIdHigh, long traceIdLow) {
+        setContextOtel0(traceIdHigh, traceIdLow, spanId);
+    }
+
     public void putCustom(int offset, int value) {
         if (offset >= MAX_CUSTOM_SLOTS) {
             throw new IllegalArgumentException("Invalid offset: " + offset + " (max " +  MAX_CUSTOM_SLOTS + ")");
@@ -215,6 +228,7 @@ public boolean setContextAttribute(int keyIndex, String value) {
     }
 
     private static native long setContext0(long spanId, long rootSpanId);
+    private static native void setContextOtel0(long traceIdHigh, long traceIdLow, long spanId);
     private static native void setContextSlot0(int offset, int value);
     private static native boolean setContextAttribute0(int keyIndex, String value);