test(execution): make the split test independent of the compaction threshold

Built the oversized batch from one huge string, which compaction offloads to a
tiny ref as soon as the value threshold drops below it — leaving the batch under
the single-write cap and the test silently exercising nothing. Build it from many
modest fields instead, which stay inline at any threshold.

Author: waleedlatif1

apps/sim/lib/execution/event-buffer.test.ts

@@ -410,12 +410,21 @@ describe('execution event buffer', () => {
    */
   it('splits a batch that exceeds the single-write cap instead of stalling on it', async () => {
     mockRedis.incrby.mockResolvedValue(100)
-    // Each event stays under the 8MiB per-event cap; two of them do not.
-    const bigPayload = 'x'.repeat(2_500_000)
+    // Built from many modest fields rather than one huge one: compaction offloads
+    // individual values over its threshold, so a single large string would leave a
+    // tiny ref behind and never reach the batch cap. Each event stays under the
+    // 8MiB per-event cap; two of them do not.
+    const chunk = 'x'.repeat(100_000)
+    const wideEvent = () => {
+      const event = makeEvent('wide')
+      const data = event.data as Record<string, unknown>
+      for (let i = 0; i < 45; i++) data[`field${i}`] = chunk
+      return event
+    }
 
     const writer = createExecutionEventWriter('exec-1')
-    await writer.write(makeEvent(bigPayload))
-    await writer.write(makeEvent(bigPayload))
+    await writer.write(wideEvent())
+    await writer.write(wideEvent())
     await writer.flush()
 
     expect(persistedEntries).toHaveLength(2)