test(git-worktree): fix test pollution from incomplete fs mock

Replace mock.module with spyOn + mockRestore to prevent fs module
pollution across test files. mock.module replaces the entire module
and caused 69 test failures in other files that depend on fs.

src/shared/git-worktree/collect-git-diff-stats.test.ts

@@ -1,79 +1,79 @@
 /// <reference types="bun-types" />
 
-import { describe, expect, mock, test } from "bun:test"
-
-const execSyncMock = mock(() => {
-  throw new Error("execSync should not be called")
-})
-
-const execFileSyncMock = mock((file: string, args: string[], _opts: { cwd?: string }) => {
-  if (file !== "git") throw new Error(`unexpected file: ${file}`)
-  const subcommand = args[0]
-
-  if (subcommand === "diff") {
-    return "1\t2\tfile.ts\n"
-  }
-
-  if (subcommand === "status") {
-    return " M file.ts\n?? new-file.ts\n"
-  }
-
-  if (subcommand === "ls-files") {
-    return "new-file.ts\n"
-  }
-
-  throw new Error(`unexpected args: ${args.join(" ")}`)
-})
-
-const readFileSyncMock = mock((_path: string, _encoding: string) => {
-  return "line1\nline2\nline3\nline4\nline5\nline6\nline7\nline8\nline9\nline10\n"
-})
-
-mock.module("node:child_process", () => ({
-  execSync: execSyncMock,
-  execFileSync: execFileSyncMock,
-}))
-
-mock.module("node:fs", () => ({
-  readFileSync: readFileSyncMock,
-}))
-
-const { collectGitDiffStats } = await import("./collect-git-diff-stats")
+import { describe, expect, test, spyOn, beforeEach, afterEach } from "bun:test"
+import * as childProcess from "node:child_process"
+import * as fs from "node:fs"
 
 describe("collectGitDiffStats", () => {
-  test("uses execFileSync with arg arrays (no shell injection)", () => {
+  let execFileSyncSpy: ReturnType<typeof spyOn>
+  let execSyncSpy: ReturnType<typeof spyOn>
+  let readFileSyncSpy: ReturnType<typeof spyOn>
+
+  beforeEach(() => {
+    execSyncSpy = spyOn(childProcess, "execSync").mockImplementation(() => {
+      throw new Error("execSync should not be called")
+    })
+
+    execFileSyncSpy = spyOn(childProcess, "execFileSync").mockImplementation(
+      ((file: string, args: string[], _opts: { cwd?: string }) => {
+        if (file !== "git") throw new Error(`unexpected file: ${file}`)
+        const subcommand = args[0]
+
+        if (subcommand === "diff") return "1\t2\tfile.ts\n"
+        if (subcommand === "status") return " M file.ts\n?? new-file.ts\n"
+        if (subcommand === "ls-files") return "new-file.ts\n"
+
+        throw new Error(`unexpected args: ${args.join(" ")}`)
+      }) as typeof childProcess.execFileSync
+    )
+
+    readFileSyncSpy = spyOn(fs, "readFileSync").mockImplementation(
+      ((_path: unknown, _encoding: unknown) => {
+        return "line1\nline2\nline3\nline4\nline5\nline6\nline7\nline8\nline9\nline10\n"
+      }) as typeof fs.readFileSync
+    )
+  })
+
+  afterEach(() => {
+    execSyncSpy.mockRestore()
+    execFileSyncSpy.mockRestore()
+    readFileSyncSpy.mockRestore()
+  })
+
+  test("uses execFileSync with arg arrays (no shell injection)", async () => {
     //#given
+    const { collectGitDiffStats } = await import("./collect-git-diff-stats")
     const directory = "/tmp/safe-repo;touch /tmp/pwn"
 
     //#when
     const result = collectGitDiffStats(directory)
 
     //#then
-    expect(execSyncMock).not.toHaveBeenCalled()
-    expect(execFileSyncMock).toHaveBeenCalledTimes(3)
+    expect(execSyncSpy).not.toHaveBeenCalled()
+    expect(execFileSyncSpy).toHaveBeenCalledTimes(3)
 
-    const [firstCallFile, firstCallArgs, firstCallOpts] = execFileSyncMock.mock
+    const [firstCallFile, firstCallArgs, firstCallOpts] = execFileSyncSpy.mock
       .calls[0]! as unknown as [string, string[], { cwd?: string }]
     expect(firstCallFile).toBe("git")
     expect(firstCallArgs).toEqual(["diff", "--numstat", "HEAD"])
     expect(firstCallOpts.cwd).toBe(directory)
     expect(firstCallArgs.join(" ")).not.toContain(directory)
 
-    const [secondCallFile, secondCallArgs, secondCallOpts] = execFileSyncMock.mock
+    const [secondCallFile, secondCallArgs, secondCallOpts] = execFileSyncSpy.mock
       .calls[1]! as unknown as [string, string[], { cwd?: string }]
     expect(secondCallFile).toBe("git")
     expect(secondCallArgs).toEqual(["status", "--porcelain"])
     expect(secondCallOpts.cwd).toBe(directory)
     expect(secondCallArgs.join(" ")).not.toContain(directory)
 
-    const [thirdCallFile, thirdCallArgs, thirdCallOpts] = execFileSyncMock.mock
+    const [thirdCallFile, thirdCallArgs, thirdCallOpts] = execFileSyncSpy.mock
       .calls[2]! as unknown as [string, string[], { cwd?: string }]
     expect(thirdCallFile).toBe("git")
     expect(thirdCallArgs).toEqual(["ls-files", "--others", "--exclude-standard"])
     expect(thirdCallOpts.cwd).toBe(directory)
     expect(thirdCallArgs.join(" ")).not.toContain(directory)
 
-    expect(readFileSyncMock).toHaveBeenCalled()
+    expect(readFileSyncSpy).toHaveBeenCalled()
 
     expect(result).toEqual([
       {