datalog: refresh module headers (findall, 6 demos)

lib/datalog/aggregates.sx

@@ -1,11 +1,12 @@
-;; lib/datalog/aggregates.sx — count / sum / min / max aggregation.
+;; lib/datalog/aggregates.sx — count / sum / min / max / findall.
 ;;
-;; Surface form (always 3-arg in the parsed AST):
+;; Surface form (always 3-arg after the relation name):
 ;;
-;;   (count  Result  Var  GoalLit)
-;;   (sum    Result  Var  GoalLit)
-;;   (min    Result  Var  GoalLit)
-;;   (max    Result  Var  GoalLit)
+;;   (count   Result  Var  GoalLit)
+;;   (sum     Result  Var  GoalLit)
+;;   (min     Result  Var  GoalLit)
+;;   (max     Result  Var  GoalLit)
+;;   (findall List    Var  GoalLit)
 ;;
 ;; Parsed naturally because arg-position compounds are already allowed
 ;; (Phase 4 needs them for arithmetic). At evaluation time the aggregator

lib/datalog/demo.sx

@@ -6,11 +6,15 @@
 ;; below show the shape of queries we want, and the test suite runs
 ;; them against synthetic in-memory tuples loaded via dl-program-data.
 ;;
-;; Three thematic demos:
+;; Six thematic demos:
 ;;
-;;   1. Federation — follow graph, transitive reach, mutuals.
-;;   2. Content   — posts, tags, likes, popularity, "for you" feed.
+;;   1. Federation — follow graph, transitive reach, mutuals, FOAF.
+;;   2. Content    — posts, tags, likes, popularity, "for you" feed.
 ;;   3. Permissions — group membership and resource access.
+;;   4. Cooking-posts — canonical "posts about cooking by people I
+;;                      follow (transitively)" multi-domain query.
+;;   5. Tag co-occurrence — distinct (T1, T2) pairs with counts.
+;;   6. Shortest path  — weighted-DAG path enumeration + min agg.
 
 ;; ── Demo 1: federation follow graph ─────────────────────────────
 ;; EDB: (follows ACTOR-A ACTOR-B) — A follows B.