native-android test writes later-offload.apk into the working directory #3705

Problem

pnpm test leaves an untracked later-offload.apk (15 bytes) in the repository root. It can be committed by accident; it was nearly staged twice while working on #3685 and #3686.

Evidence

packages/stim-cli/src/__tests__/native-android.test.ts is the only source that names later-offload.apk. After a full pnpm test, git status shows ?? later-offload.apk.

Cause

A case in that test writes the file relative to the process working directory instead of a temporary directory.

Fix idea

Write it under a temporary directory the test removes.