datalog: semi-naive saturator + delta sets (Phase 5, 114/114)

dl-saturate! is now semi-naive: tracks a per-relation delta dict,
and on each iteration walks every positive body-literal position,
substituting the delta of its relation while joining the rest
against the previous-iteration DB. Candidates are collected before
mutating the DB so the "full" sides see a consistent snapshot.
Rules with no positive body literal (e.g. (p X) :- (= X 5).)
fall back to a one-shot naive pass via dl-collect-rule-candidates.

dl-saturate-naive! retained as the reference implementation; 8
differential tests compare per-relation tuple counts on every
recursive program. Switched dl-tuple-member? to indexed iteration
instead of recursive rest (eliminates per-step list copy). Larger
chains under bundled conformance trip O(n) membership × CPU
sharing — added a Blocker to swap relations to hash-set membership.

lib/datalog/scoreboard.json

@@ -1,14 +1,15 @@
 {
   "lang": "datalog",
-  "total_passed": 106,
+  "total_passed": 114,
   "total_failed": 0,
-  "total": 106,
+  "total": 114,
   "suites": [
     {"name":"tokenize","passed":26,"failed":0,"total":26},
     {"name":"parse","passed":18,"failed":0,"total":18},
     {"name":"unify","passed":28,"failed":0,"total":28},
     {"name":"eval","passed":15,"failed":0,"total":15},
-    {"name":"builtins","passed":19,"failed":0,"total":19}
+    {"name":"builtins","passed":19,"failed":0,"total":19},
+    {"name":"semi_naive","passed":8,"failed":0,"total":8}
   ],
-  "generated": "2026-05-07T23:50:44+00:00"
+  "generated": "2026-05-08T08:12:42+00:00"
 }