Datasheet: describe what the verifier does, and record the interpreter used

DATASHEET.md

@@ -122,8 +122,13 @@ genuine defect.
 
 **Independent re-verification.** `verify.py` re-clones each project from scratch,
 checks out both commits, re-applies the fix commit's tests and runs them again. It
-shares no code with the pipeline that produced the corpus, so it would catch a
-mistake the pipeline made rather than merely agreeing with it.
+reads only the published record and the project it cites, and re-derives the
+result from the upstream repository.
+
+Old projects are run under an interpreter that can import them, so a record from
+2016 is not judged by whether it works on a current Python. The interpreter used
+is reported alongside the verdict. A record that cannot be run on a given machine
+is reported as skipped, never as a failure.
 
 ```bash
 python3 verify.py --sample 20