test(features): update background agent, MCP loader, and tmux tests

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/features/background-agent/compaction-aware-message-resolver.test.ts

@@ -11,7 +11,7 @@ import {
   clearCompactionAgentConfigCheckpoint,
   setCompactionAgentConfigCheckpoint,
 } from "../../shared/compaction-agent-config-checkpoint"
-import { PART_STORAGE } from "../../shared"
+import { getCompactionPartStorageDir } from "../../shared/compaction-marker"
 
 describe("isCompactionAgent", () => {
   describe("#given agent name variations", () => {
@@ -74,7 +74,7 @@ describe("findNearestMessageExcludingCompaction", () => {
 
   afterEach(() => {
     rmSync(tempDir, { force: true, recursive: true })
-    rmSync(join(PART_STORAGE, "msg_test_background_compaction_marker"), { force: true, recursive: true })
+    rmSync(getCompactionPartStorageDir("msg_test_background_compaction_marker"), { force: true, recursive: true })
     clearCompactionAgentConfigCheckpoint("ses_checkpoint")
   })
 
@@ -121,7 +121,7 @@ describe("findNearestMessageExcludingCompaction", () => {
     test("skips JSON messages whose part storage contains a compaction marker", () => {
       // given
       const compactionMessageID = "msg_test_background_compaction_marker"
-      const partDir = join(PART_STORAGE, compactionMessageID)
+      const partDir = getCompactionPartStorageDir(compactionMessageID)
       writeFileSync(join(tempDir, "002.json"), JSON.stringify({
         id: compactionMessageID,
         agent: "atlas",

src/features/background-agent/manager.test.ts

@@ -12,6 +12,7 @@ import { MIN_IDLE_TIME_MS } from "./constants"
 import { BackgroundManager } from "./manager"
 import { ConcurrencyManager } from "./concurrency"
 import { initTaskToastManager, _resetTaskToastManagerForTesting } from "../task-toast-manager/manager"
+import { _resetForTesting as resetProcessCleanupState } from "./process-cleanup"
 
 mock.module("../../shared/connected-providers-cache", () => ({
   readConnectedProvidersCache: () => null,
@@ -1933,6 +1934,7 @@ describe("BackgroundManager.resume model persistence", () => {
 describe("BackgroundManager process cleanup", () => {
   test("should remove listeners after last shutdown", () => {
     // given
+    resetProcessCleanupState()
     const signals = getCleanupSignals()
     const baseline = getListenerCounts(signals)
     const managerA = createBackgroundManager()
@@ -1951,6 +1953,8 @@ describe("BackgroundManager process cleanup", () => {
       expect(afterFirstShutdown[signal]).toBe(baseline[signal] + 1)
       expect(afterSecondShutdown[signal]).toBe(baseline[signal])
     }
+
+    resetProcessCleanupState()
   })
 })