test: final source recheck for V1 jet CV and V3 Taylor-Green runs

Both runners now re-derive the recorded source identity after the run
(source_provenance.final_source_check) and only then mark the receipt
complete. A changed source, or a recheck that fails, rewrites the receipt
as invalid and raises:
- V1: in-run receipts carry run_status=INCOMPLETE; finish_receipt sets
  COMPLETE or INVALID_SOURCE_CHANGED (+ source_recheck/source_after).
- V3: completed stays False, invalid=SOURCE_CHANGED_DURING_RUN, no
  screening_pass; the assessor requires source_recheck UNCHANGED (frozen
  mode still accepts receipts from before the field existed).
Interrupted runs keep INCOMPLETE / completed=False. Host tests cover
unchanged, changed and failed rechecks and incomplete runs. No threshold
or solver change.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/validation/taylor_green/run_case.py

@@ -319,6 +319,17 @@ def main():
                         ),
                         flush=True,
                     )
+    from tests.validation.source_provenance import final_source_check
+    recheck = final_source_check(
+        dict(source=source, runtime_source=runtime),
+        lambda: dict(source=verify_source(repo, args.expected_revision,
+                                          current=args.current_checkout),
+                     runtime_source=runtime_source(repo)))
+    report.update(recheck)
+    if recheck["source_recheck"] != "UNCHANGED":
+        report.update(invalid="SOURCE_CHANGED_DURING_RUN")  # completed stays False
+        save()
+        raise RuntimeError("Source changed during the run; receipt marked invalid")
     report.update(
         completed=True,
         seconds=time.monotonic() - started,