fix(ci): resolve mock.module() cross-file leakage in test suite

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

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

src/features/background-agent/abort-with-timeout.test.ts

@@ -6,9 +6,11 @@ mock.module("../../shared", () => ({
   log: logMock,
 }))
 
-import { abortWithTimeout } from "./abort-with-timeout"
 import type { OpencodeClient } from "./opencode-client"
 
+const { abortWithTimeout } = await import("./abort-with-timeout")
+mock.restore()
+
 function createClient(abort: (...args: Array<unknown>) => Promise<unknown>): OpencodeClient {
   return {
     session: {

src/features/background-agent/fallback-retry-handler.test.ts

@@ -17,14 +17,15 @@ mock.module("../../shared/provider-model-id-transform", () => ({
   transformModelForProvider: mock((_provider: string, model: string) => model),
 }))
 
-import { tryFallbackRetry } from "./fallback-retry-handler"
-import { shouldRetryError } from "../../shared/model-error-classifier"
-import { selectFallbackProvider } from "../../shared/model-error-classifier"
-import { readProviderModelsCache } from "../../shared"
 import type { BackgroundTask } from "./types"
 import type { ConcurrencyManager } from "./concurrency"
 import type { OpencodeClient, QueueItem } from "./constants"
 
+const { tryFallbackRetry } = await import("./fallback-retry-handler")
+const { shouldRetryError, selectFallbackProvider } = await import("../../shared/model-error-classifier")
+const { readProviderModelsCache } = await import("../../shared")
+mock.restore()
+
 function createDeferredPromise(): {
   promise: Promise<void>
   resolve: () => void

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

@@ -20,6 +20,7 @@ import { MIN_IDLE_TIME_MS } from "./constants"
 import { BackgroundManager } from "./manager"
 import { ConcurrencyManager } from "./concurrency"
 import { initTaskToastManager, _resetTaskToastManagerForTesting } from "../task-toast-manager/manager"
+mock.restore()
 
 
 const TASK_TTL_MS = 30 * 60 * 1000

src/features/background-agent/session-status-classifier.test.ts

@@ -1,11 +1,13 @@
 import { describe, test, expect, mock, afterAll } from "bun:test"
-import { isActiveSessionStatus, isTerminalSessionStatus } from "./session-status-classifier"
 
 const mockLog = mock()
 mock.module("../../shared", () => ({ log: mockLog }))
 
 afterAll(() => { mock.restore() })
 
+const { isActiveSessionStatus, isTerminalSessionStatus } = await import("./session-status-classifier")
+mock.restore()
+
 describe("isActiveSessionStatus", () => {
   describe("#given a known active session status", () => {
     test('#when type is "busy" #then returns true', () => {