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>

CREDITS.md

@@ -5,5 +5,8 @@
 - License: **Creative Commons Attribution 4.0 International (CC BY 4.0)** – https://creativecommons.org/licenses/by/4.0/
 - File: `assets/dbyte_1x.png` (unmodified). In the game it is scaled by integer factors and tinted. The swapped glyphs ö/ò are corrected in the character mapping, not in the file.
 
+## Made with Claude Code
+The game was developed with the help of [Claude Code](https://claude.com/claude-code), Anthropic's AI coding assistant. The small pixel-art mark next to the note on the title and login screens is a rendition of the Claude Code logo. Claude, Claude Code and Anthropic are trademarks of Anthropic; the mark only credits the tool and is not covered by the MIT licence of this project.
+
 ## Everything else
 Code, procedural graphics and game design: the DungeonCraft project.