Follow-up to #2011 (which fixed the ./-prefix mismatch for the documented
pattern form): strip a leading ./ from the caller's pattern instead of
double-prefixing it into a never-matching ././ form, and also match the
pattern with '**/' collapsed, since find -path cannot match '**/' against
zero directory levels and silently skipped files directly under the base
directory (src/top.test.ts vs src/**/*.test.ts).
Adds a deterministic test suite for the script with a stubbed npm.
