Credit Claude Code: note at the top of the README, in CREDITS and the standalone file; pixel-art mark with link next to the licence on title and login screens

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/main.rs

@@ -792,6 +792,7 @@ async fn main() {
                         autosave_t = 0.0;
                     }
                     MenuAction::OpenRepo => platform::open_url(menu::REPO_URL),
+                    MenuAction::OpenClaudeCode => platform::open_url(menu::CLAUDE_CODE_URL),
                     a @ (MenuAction::Login(..)
                     | MenuAction::Logout
                     | MenuAction::OpenAccount