datalog: dl-query accepts conjunctive goal lists (167/167)

dl-query now auto-dispatches on the first element's shape:
- positive literal (head is a symbol) or {:neg ...} dict → wrap
- list of literals → conjunctive query

dl-query-coerce normalizes; dl-query-user-vars collects the union
of user-named vars (deduped, '_' filtered) for projection. Old
single-literal callers unchanged.

  (dl-query db '(p X))                   ; single
  (dl-query db '((p X) (q X)))           ; conjunction
  (dl-query db (list '(n X) '(> X 2)))   ; with comparison

2 new api tests cover multi-goal AND and conjunction with comparison.

lib/datalog/eval.sx

@@ -362,32 +362,72 @@
 
 ;; ── Querying ─────────────────────────────────────────────────────
 
+;; Coerce a query argument to a list of body literals. A single literal
+;; like `(p X)` (positive — head is a symbol) or `{:neg ...}` becomes
+;; `((p X))`. A list of literals like `((p X) (q X))` is returned as-is.
+(define
+  dl-query-coerce
+  (fn
+    (goal)
+    (cond
+      ((and (dict? goal) (has-key? goal :neg)) (list goal))
+      ((and (list? goal) (> (len goal) 0) (symbol? (first goal)))
+        (list goal))
+      ((list? goal) goal)
+      (else (error (str "dl-query: unrecognised goal shape: " goal))))))
+
 (define
   dl-query
   (fn
     (db goal)
     (do
       (dl-saturate! db)
-      ;; Rename anonymous '_' vars in the goal so multiple occurrences
-      ;; do not unify together. Keep the user-facing var list (taken
-      ;; before renaming) so projected results retain user names.
+      ;; Rename anonymous '_' vars in each goal literal so multiple
+      ;; occurrences do not unify together. Keep the user-facing var
+      ;; list (taken before renaming) so projected results retain user
+      ;; names.
       (let
-        ((user-vars (filter (fn (n) (not (= n "_"))) (dl-vars-of goal)))
-          (renamed (dl-rename-anon-lit goal (dl-make-anon-renamer))))
+        ((goals (dl-query-coerce goal))
+          (renamer (dl-make-anon-renamer)))
         (let
-          ((substs (dl-find-bindings (list renamed) db (dl-empty-subst)))
-            (results (list)))
-          (do
-            (for-each
-              (fn
-                (s)
-                (let
-                  ((proj (dl-project-subst s user-vars)))
+          ((user-vars (dl-query-user-vars goals))
+            (renamed (map (fn (g) (dl-rename-anon-lit g renamer)) goals)))
+          (let
+            ((substs (dl-find-bindings renamed db (dl-empty-subst)))
+              (results (list)))
+            (do
+              (for-each
+                (fn
+                  (s)
+                  (let
+                    ((proj (dl-project-subst s user-vars)))
+                    (when
+                      (not (dl-tuple-member? proj results))
+                      (append! results proj))))
+                substs)
+              results)))))))
+
+(define
+  dl-query-user-vars
+  (fn
+    (goals)
+    (let ((seen (list)))
+      (do
+        (for-each
+          (fn
+            (g)
+            (let
+              ((tgt
+                 (if (and (dict? g) (has-key? g :neg)) (get g :neg) g)))
+              (for-each
+                (fn
+                  (v)
                   (when
-                    (not (dl-tuple-member? proj results))
-                    (append! results proj))))
-              substs)
-            results))))))
+                    (and (not (= v "_")) (not (dl-member-string? v seen)))
+                    (append! seen v)))
+                (dl-vars-of tgt))))
+          goals)
+        seen))))
 
 (define
   dl-project-subst