fix(event): prune synthetic idle dedup map

src/plugin/recent-synthetic-idles.test.ts

@@ -0,0 +1,24 @@
+import { describe, it, expect } from "bun:test"
+
+import { pruneRecentSyntheticIdles } from "./recent-synthetic-idles"
+
+describe("pruneRecentSyntheticIdles", () => {
+  it("removes entries older than dedup window", () => {
+    // given
+    const recentSyntheticIdles = new Map<string, number>([
+      ["ses_old", 1000],
+      ["ses_new", 1600],
+    ])
+
+    // when
+    pruneRecentSyntheticIdles({
+      recentSyntheticIdles,
+      now: 2000,
+      dedupWindowMs: 500,
+    })
+
+    // then
+    expect(recentSyntheticIdles.has("ses_old")).toBe(false)
+    expect(recentSyntheticIdles.has("ses_new")).toBe(true)
+  })
+})