Remove Gemfile.lock from version control

Gems should not commit their lockfile, as it pins dependency
versions that conflict with CI's Ruby/gem matrix.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: aflanagan

.gitignore

@@ -9,3 +9,5 @@
 
 # rspec failure tracking
 .rspec_status
+
+Gemfile.lock