Build a browser and controller compatibility matrix

[Swarek]

Goal

Create a small, repeatable browser and controller compatibility matrix for the hosted public build.

Acceptance criteria

• Cover current Chrome, Firefox, Safari, and Edge on at least two desktop operating systems.
• Test keyboard-only play, one controller, and two controllers where available.
• Record controller detection, cursor navigation, custom bindings, a complete match, and persistence after reload.
• Use only the public build and open content in evidence.
• Document reproducible failures as separate bug reports.
• Publish the matrix in a concise contributor-facing document.