fix(event): prune synthetic idle dedup map

src/plugin/recent-synthetic-idles.ts

@@ -0,0 +1,13 @@
+export function pruneRecentSyntheticIdles(args: {
+  recentSyntheticIdles: Map<string, number>
+  now: number
+  dedupWindowMs: number
+}): void {
+  const { recentSyntheticIdles, now, dedupWindowMs } = args
+
+  for (const [sessionID, emittedAt] of recentSyntheticIdles) {
+    if (now - emittedAt >= dedupWindowMs) {
+      recentSyntheticIdles.delete(sessionID)
+    }
+  }
+}