chore: gitignore .tool-versions (asdf)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.gitignore

@@ -138,3 +138,6 @@ tools/cartridge-minter/target/
 
 # panic-attack scan reports
 panic-attack-report*.json
+
+# asdf version manager
+.tool-versions