Use the class rejection helper in the SF segment tests

The two storeAndForwardMaxSegmentBytes rejection tests spelled out
try/fail/catch inline, 19 lines for what the class already expresses in
one call. assertThrows(String, Runnable) is the dominant idiom here,
used by roughly twenty other tests in the file, and it produces a
better failure message than a bare Assert.fail.

The assertion moves from message equality to containment. The expected
text is the whole message in both cases, so the check is as strong as
it was; a mutation run with both production guards removed fails both
tests.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: mtopolnik

core/src/test/java/io/questdb/client/test/cutlass/qwp/client/LineSenderBuilderWebSocketTest.java

@@ -649,16 +649,8 @@ public void testStoreAndForwardMaxSegmentBytes() {
     public void testStoreAndForwardMaxSegmentBytesRejectsNonPositiveValues() {
         long[] rejected = {0L, -1L};
         for (long value : rejected) {
-            try {
-                Sender.builder(Sender.Transport.WEBSOCKET)
-                        .storeAndForwardMaxSegmentBytes(value);
-                Assert.fail("expected storeAndForwardMaxSegmentBytes(" + value + ") to fail");
-            } catch (LineSenderException expected) {
-                Assert.assertEquals(
-                        "sf_max_segment_bytes must be positive: " + value,
-                        expected.getMessage()
-                );
-            }
+            assertThrows("sf_max_segment_bytes must be positive: " + value,
+                    () -> Sender.builder(Sender.Transport.WEBSOCKET).storeAndForwardMaxSegmentBytes(value));
         }
     }
 
@@ -670,15 +662,8 @@ public void testStoreAndForwardMaxSegmentBytesRejectedForNonWebSocketTransports(
                 Sender.Transport.UDP
         };
         for (Sender.Transport transport : rejected) {
-            try {
-                Sender.builder(transport).storeAndForwardMaxSegmentBytes(64 * 1024L);
-                Assert.fail("expected " + transport + " to reject storeAndForwardMaxSegmentBytes");
-            } catch (LineSenderException expected) {
-                Assert.assertEquals(
-                        "store_and_forward is only supported for WebSocket transport",
-                        expected.getMessage()
-                );
-            }
+            assertThrows("store_and_forward is only supported for WebSocket transport",
+                    () -> Sender.builder(transport).storeAndForwardMaxSegmentBytes(64 * 1024L));
         }
     }