Use package-friendly runtime paths

[besendorf]

Summary

• Extract bundled ADB assets into a private temporary directory instead of next to the androidqf executable.
• Keep generated acquisition output in the current working directory, including encrypted archives.
• Look for key.txt in the current working directory first, then fall back to the executable directory.
• Document the new output and key lookup behavior and add focused tests.

Why

This is better for androidqf usage when it is installed via a package manager: packaged executables usually live in read-only or shared system locations, while runtime artifacts should be written to the user's working directory or a temporary directory.