Docs: proofread the English public-site copy

[Codewriter90x]

Goal

Proofread the English copy in the public website for clarity, grammar, and consistency with the Italian version.

Scope

• navigation and hero copy;
• feature and learning-path sections;
• source-only download wording;
• licensing, FAQ, and footer copy.

Acceptance criteria

• Technical claims remain accurate.
• Source-only and no-public-binaries wording remains intact.
• No gameplay capability is promised unless it exists in the repository.
• The patch changes copy only, unless a tiny accessibility attribute correction is necessary.