datalog: stratifier rejects recursion through aggregation (165/165)

Bug: dl-check-stratifiable iterated body literals looking only for
explicit :neg literals, missing aggregate cycles. Now also walks
aggregates via dl-aggregate-dep-edge — q(N) :- count(N, X, q(X))
correctly errors out at saturation time.

3 new tests cover:
- recursion-through-aggregation rejected
- negation + aggregation coexist when in different strata
- min over empty derived relation produces no result

lib/datalog/scoreboard.json

@@ -1,8 +1,8 @@
 {
   "lang": "datalog",
-  "total_passed": 162,
+  "total_passed": 165,
   "total_failed": 0,
-  "total": 162,
+  "total": 165,
   "suites": [
     {"name":"tokenize","passed":26,"failed":0,"total":26},
     {"name":"parse","passed":18,"failed":0,"total":18},
@@ -11,9 +11,9 @@
     {"name":"builtins","passed":19,"failed":0,"total":19},
     {"name":"semi_naive","passed":8,"failed":0,"total":8},
     {"name":"negation","passed":10,"failed":0,"total":10},
-    {"name":"aggregates","passed":13,"failed":0,"total":13},
+    {"name":"aggregates","passed":16,"failed":0,"total":16},
     {"name":"api","passed":9,"failed":0,"total":9},
     {"name":"demo","passed":13,"failed":0,"total":13}
   ],
-  "generated": "2026-05-08T09:05:25+00:00"
+  "generated": "2026-05-08T09:12:57+00:00"
 }