chore(naming): footer canonique -> K7 (formerly GIFT), identite current

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: gift-framework

README.md

@@ -92,6 +92,6 @@ dated, against scheduled experimental data.
 
 ---
 
-<sub>GIFT is the founding framework of the Arithmon program.
+<sub>K₇ (formerly GIFT) is the founding framework of the Arithmon program.
 Program: [arithmon.com](https://arithmon.com) ·
 [github.com/arithmon](https://github.com/arithmon)</sub>