Switch durable-ack fuzz to QuestDB Rnd + TestUtils.generateRandom

Use the project's Rnd and the generateRandom helper instead of a raw
java.util.Random. generateRandom logs the (s0, s1) seed pair to stdout,
which is the project-standard repro recipe -- a flake in CI now leaves
the exact seeds in the test output, and operators reproduce by passing
them back into TestUtils.generateRandom(null, s0, s1).

The AssertionError on fuzz failure also includes both seeds, so the
repro recipe is co-located with the failure stack rather than buried
in surrounding stdout that may or may not survive CI log retention.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: bluestreak01

core/src/test/java/io/questdb/client/test/cutlass/qwp/client/sf/cursor/CursorWebSocketSendLoopDurableAckFuzzTest.java

@@ -29,6 +29,7 @@
 import io.questdb.client.cutlass.qwp.client.sf.cursor.CursorWebSocketSendLoop;
 import io.questdb.client.std.Files;
 import io.questdb.client.std.MemoryTag;
+import io.questdb.client.std.Rnd;
 import io.questdb.client.std.Unsafe;
 import io.questdb.client.test.tools.TestUtils;
 import org.junit.After;
@@ -42,7 +43,6 @@
 import java.nio.file.Paths;
 import java.util.HashMap;
 import java.util.Map;
-import java.util.Random;
 
 /**
  * Randomised stress test for the durable-ack-driven trim path. Generates a
@@ -56,7 +56,6 @@
  */
 public class CursorWebSocketSendLoopDurableAckFuzzTest {
 
-    private static final long DEFAULT_SEED = -1L;
     private static final int ITERATIONS = 500;
     private static final int MAX_FRAMES = 64;
     private static final String[] TABLE_POOL = {"trades", "orders", "fills", "positions"};
@@ -92,15 +91,21 @@ public void tearDown() {
     }
 
     @Test
-    public void testFuzzInvariantHolds() throws Exception {
-        long seed = DEFAULT_SEED == -1L ? System.nanoTime() : DEFAULT_SEED;
-        Random rnd = new Random(seed);
+    public void testFuzzInvariantHolds() {
+        // Capture both seeds so a fuzz failure prints a reproducer the
+        // operator can plug straight back into TestUtils.generateRandom(
+        // null, s0, s1). generateRandom also prints them on its own, but
+        // including them in the AssertionError message keeps the repro
+        // recipe co-located with the failure in CI logs.
+        long s0 = System.nanoTime();
+        long s1 = System.currentTimeMillis();
+        Rnd rnd = TestUtils.generateRandom(null, s0, s1);
         try {
             for (int iter = 0; iter < ITERATIONS; iter++) {
                 runOneIteration(rnd, iter);
             }
         } catch (Throwable t) {
-            throw new AssertionError("fuzz failure with seed=" + seed, t);
+            throw new AssertionError("fuzz failure with seeds=" + s0 + "L," + s1 + "L", t);
         }
     }
 
@@ -167,7 +172,7 @@ private static void deliver(CursorWebSocketSendLoop loop, long packed) throws Ex
         }
     }
 
-    private static void runOneIteration(Random rnd, int iter) throws Exception {
+    private static void runOneIteration(Rnd rnd, int iter) throws Exception {
         // Pre-build: pick frame count, per-batch tables. Track expected
         // (table, seqTxn) so the fuzz oracle can compute the contiguous
         // durable prefix at any point.