chore: gitignore .tool-versions (asdf)

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

Author: hyperpolymath

.gitignore

@@ -122,3 +122,6 @@ Thumbs.db
 # ── Dependencies ────────────────────────────────────────
 /vendor/
 /deps/
+
+# asdf version manager
+.tool-versions