On a fork without an 'upstream' remote, the checker silently fell back to 'origin' (the fork itself) and still printed '[OK] All framework files are up to date with upstream!', a false positive: the fork is always up to date with itself, so upstream updates were never reported. This is exactly the setup CONTRIBUTING.md recommends for forks.
Now, when the fallback remote does not point at the ai-job-search template repo, the script warns that the comparison is fork-vs-self and prints the command to add the template as a remote. The final OK line now names the ref it actually compared against.
Tests (new tests/test_check_upstream_updates.py, three scenarios) fail on master and pass with the fix.
