fix: Windows build — wait for the sidecar to exit before removing its temp dir (v0.2.134)

[raylanlin]

What broke

Build Windows Installer run 36976756947 stopped in npm test. Of 202 tests, 201 passed. The failure was in the after hook of tests/sidecar-client.test.mjs:

EBUSY: resource busy or locked, rmdir 'C:\Users\RUNNER~1\AppData\Local\Temp\mw-sidecar-60rVgZ'

On Windows, ChildProcess.kill() returns before the Python sidecar has actually exited. Windows also refuses to delete a folder that a live process is using as its working directory. The hook deleted that folder right after stop(), so it hit EBUSY.

Ubuntu CI (ci.yml) cannot catch this because Linux allows the delete. Earlier Windows runs passed only because the process happened to exit in time.

Fix (test only, app code unchanged)

• The hook now waits for the sidecar process's exit event before cleaning up, with a 5 s cap.
• rmSync now uses maxRetries: 10, retryDelay: 200.
• If the temp folder still can't be deleted, the hook logs a warning instead of failing the test.

Checks

• npm run lint and npm run typecheck are clean.
• npm test passes all 201 tests, and no mw-sidecar-* folders are left behind.
• precommit-check.sh 0.2.134 passes.
• Build Windows Installer has been started on this branch to confirm the fix on Windows.