feat: let a reference name its variant

A reference taken from a check names the variant that ran the full set, and the test judges that variant's repetitions.

tests/campaign/oracle.yml

@@ -6,7 +6,8 @@
 #               retro_get_system_info gives): the reference frames a run with
 #               the full BIOS set reaches. Each was recorded once
 #               (`recorded_from`, the record id) and reviewed by looking at its
-#               PNG. `stage: bios` is a screen only the console's own BIOS
+#               PNG, from the variant `variant` names when that run was a
+#               check. `stage: bios` is a screen only the console's own BIOS
 #               draws, `stage: game` a screen of the content. A run that reaches
 #               one of them boots.
 # error_patterns  log lines after which a core stops, read from its source

tests/test_core_probe.py

@@ -298,7 +298,11 @@ class OracleTests(unittest.TestCase):
                 record = records.get(block["recorded_from"])
                 self.assertIsNotNone(record, f"{item['name']} on {library}: {block['recorded_from']}")
                 self.assertEqual(record["inputs"]["content"]["sha1"], item["sha1"], item["name"])
-                for rep in record["variants"][0]["repetitions"]:
+                # A check names the variant that ran the full set, a run has one.
+                label = block.get("variant")
+                chosen = next(v for v in record["variants"] if v["label"] == label) if label \
+                    else record["variants"][0]
+                for rep in chosen["repetitions"]:
                     oracle = core_probe.oracle_for(data, item["sha1"], rep["library_name"])
                     verdict, evidence = core_probe.judge(rep, oracle)
                     self.assertEqual(verdict, "boots", f"{item['name']} on {library}: {evidence}")