fix(relayBench): raise harness heap to 8g so the 1M sync phase doesn't OOM

`SyncBenchmark.effectiveEvents` materializes the whole corpus as Event objects
plus a dedup LinkedHashMap to derive the 80% slices, so a million-event run
blew past the 2g default with an OutOfMemoryError before the negentropy sync
could start. -Xmx is a ceiling, not a reservation, so smaller runs don't pay
for the higher limit; JAVA_OPTS still overrides it.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012EZeWww5TJnzBZKPoc6mvU

relayBench/build.gradle.kts

@@ -10,7 +10,11 @@ application {
     applicationName = "relaybench"
     // Percentile latencies get skewed by GC pauses in the *client* — give the
     // harness enough heap that it never becomes the bottleneck being measured.
-    applicationDefaultJvmArgs = listOf("-Xmx2g")
+    // The sync phase also materializes the whole corpus as Event objects (plus
+    // a dedup map) to derive the 80% slices, so a million-event run needs more
+    // than 2g or `SyncBenchmark.effectiveEvents` OOMs. -Xmx is a ceiling, not a
+    // reservation, so small runs don't pay for it. Override with JAVA_OPTS.
+    applicationDefaultJvmArgs = listOf("-Xmx8g")
 }
 
 kotlin {