chore: give local verification tooling a gitignored home

The pinned CI tools and the pre-push verification script were living in
a temp directory that did not survive. tmp/ is now ignored, so ruff
(which respects .gitignore by default) and the git ls-files globs the
lint jobs use both skip it without needing to be told.

.gitignore

@@ -96,6 +96,8 @@ replacements.txt
 # Temp files
 edu_master/temp/
 temp/*
+# Local-only tooling scratch space (pinned CI tools, verification scripts)
+tmp/
 
 # Environment
 .env