test(sync-continuation): add comprehensive test coverage

- Add tests for sync-continuation error paths and toast cleanup
- Add tests for sync-result-fetcher with anchor message support
- Expand sync-session-poller tests for edge cases and completion detection
- Add bulk cleanup test for recent-synthetic-idles

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

@@ -3,7 +3,7 @@ import { describe, it, expect } from "bun:test"
 import { pruneRecentSyntheticIdles } from "./recent-synthetic-idles"
 
 describe("pruneRecentSyntheticIdles", () => {
-  it("removes entries older than dedup window", () => {
+  it("removes entries where now - emittedAt >= dedupWindowMs (stale cleanup works)", () => {
     //#given
     const recentSyntheticIdles = new Map<string, number>([
       ["ses_old", 1000],
@@ -21,4 +21,113 @@ describe("pruneRecentSyntheticIdles", () => {
     expect(recentSyntheticIdles.has("ses_old")).toBe(false)
     expect(recentSyntheticIdles.has("ses_new")).toBe(true)
   })
+
+  it("preserves entries where now - emittedAt < dedupWindowMs (fresh entries kept)", () => {
+    //#given
+    const recentSyntheticIdles = new Map<string, number>([
+      ["ses_fresh_1", 1950],
+      ["ses_fresh_2", 1980],
+    ])
+
+    //#when
+    pruneRecentSyntheticIdles({
+      recentSyntheticIdles,
+      now: 2000,
+      dedupWindowMs: 100,
+    })
+
+    //#then
+    expect(recentSyntheticIdles.has("ses_fresh_1")).toBe(true)
+    expect(recentSyntheticIdles.has("ses_fresh_2")).toBe(true)
+    expect(recentSyntheticIdles.size).toBe(2)
+  })
+
+  it("handles empty Map without crashing (no-op on empty)", () => {
+    //#given
+    const recentSyntheticIdles = new Map<string, number>()
+
+    //#when
+    pruneRecentSyntheticIdles({
+      recentSyntheticIdles,
+      now: 2000,
+      dedupWindowMs: 500,
+    })
+
+    //#then
+    expect(recentSyntheticIdles.size).toBe(0)
+  })
+
+  it("removes only stale entries in mixed sessions (mixed sessions: only stale removed, fresh kept)", () => {
+    //#given
+    const recentSyntheticIdles = new Map<string, number>([
+      ["ses_stale_1", 1000],
+      ["ses_fresh_1", 1950],
+      ["ses_stale_2", 1200],
+      ["ses_fresh_2", 1980],
+    ])
+
+    //#when
+    pruneRecentSyntheticIdles({
+      recentSyntheticIdles,
+      now: 2000,
+      dedupWindowMs: 500,
+    })
+
+    //#then
+    expect(recentSyntheticIdles.has("ses_stale_1")).toBe(false)
+    expect(recentSyntheticIdles.has("ses_stale_2")).toBe(false)
+    expect(recentSyntheticIdles.has("ses_fresh_1")).toBe(true)
+    expect(recentSyntheticIdles.has("ses_fresh_2")).toBe(true)
+    expect(recentSyntheticIdles.size).toBe(2)
+  })
+
+  it("clears all entries when all are stale (all-stale → Map becomes empty)", () => {
+    //#given
+    const recentSyntheticIdles = new Map<string, number>([
+      ["ses_old_1", 500],
+      ["ses_old_2", 800],
+      ["ses_old_3", 1200],
+    ])
+
+    //#when
+    pruneRecentSyntheticIdles({
+      recentSyntheticIdles,
+      now: 2000,
+      dedupWindowMs: 500,
+    })
+
+    //#then
+    expect(recentSyntheticIdles.size).toBe(0)
+  })
+
+  it("cleans 100+ entries in single pass (bulk cleanup works)", () => {
+    //#given
+    const recentSyntheticIdles = new Map<string, number>()
+    // Add 50 stale entries
+    for (let i = 0; i < 50; i++) {
+      recentSyntheticIdles.set(`ses_stale_${i}`, 500 + i)
+    }
+    // Add 60 fresh entries
+    for (let i = 0; i < 60; i++) {
+      recentSyntheticIdles.set(`ses_fresh_${i}`, 1950 + i)
+    }
+
+    //#when
+    pruneRecentSyntheticIdles({
+      recentSyntheticIdles,
+      now: 2000,
+      dedupWindowMs: 500,
+    })
+
+    //#then
+    expect(recentSyntheticIdles.size).toBe(60)
+    // Verify all stale entries are gone
+    for (let i = 0; i < 50; i++) {
+      expect(recentSyntheticIdles.has(`ses_stale_${i}`)).toBe(false)
+    }
+    // Verify all fresh entries remain
+    for (let i = 0; i < 60; i++) {
+      expect(recentSyntheticIdles.has(`ses_fresh_${i}`)).toBe(true)
+    }
+  })
 })