Investigate portable Windows build support

[man612]

Problem

Some users may prefer running Wirebound without an installer.

Proposed work

• Check electron-builder portable target options for Windows.
• Verify bundled Gnirehtet and ADB paths still resolve in portable mode.
• Document the difference between installer and portable builds.

Verification

• Produce a portable artifact locally.
• Launch the portable app.
• Confirm bundled runtime files are found.