chore: gitignore .tool-versions (asdf)

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

Author: hyperpolymath

.gitignore

@@ -94,3 +94,6 @@ verisimdb/verisimdb-data/
 *.cmt
 *.cmti
 *.cmi
+
+# asdf version manager
+.tool-versions