feat: add integrated external tools workspace

[TrapEmAll]

Summary

• adds a dedicated External Tools workspace to the desktop sidebar
• adds a XeXTool preset for basic and extended XEX information
• supports custom user-supplied CLI executables and {input} / {output} argument templates
• previews the exact command and captures stdout/stderr in the GUI
• adds background execution, cancellation, timeout handling, and separate saved paths for XeXTool and custom tools
• executes tools directly with shell=False
• adds TrapEmAll creator attribution, GitHub profile access, and a heartfelt community message to About
• documents setup, platform behavior, redistribution boundaries, and safety guidance

Third-party software

XeXTool is integrated as a user-supplied executable because clear redistribution permission could not be established. No XeXTool binary, proprietary SDK content, firmware, keys, or commercial game content is included. The generic runner provides a clean foundation for adding other lawfully obtained community utilities.

Community message

The About page now presents UnityScraper as TrapEmAll's way of giving back to the developers, archivists, modders, testers, and players who continue to preserve Xbox 360 knowledge and history.

Validation

• 78 tests passed
• Ruff passed across the repository
• focused mypy checks passed
• compileall and desktop imports passed
• About attribution assertions passed
• hidden Windows Tk smoke test constructed the XeXTool workspace successfully
• command-runner tests verify that shell metacharacters remain plain argument data

Platform notes

Native command-line tools work on their supported operating systems. UnityScraper does not automatically install or invoke Wine for Windows-only executables on Linux.