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/tests/api.sx

@@ -180,6 +180,24 @@
             (dl-query db (quote (p X)))))
         (list {:X 1} {:X 2}))
 
+      ;; Multi-goal query: pass list of literals.
+      (dl-api-test-set! "multi-goal query"
+        (dl-query
+          (dl-program-data
+            (quote ((p 1) (p 2) (p 3) (q 2) (q 3)))
+            (list))
+          (list (quote (p X)) (quote (q X))))
+        (list {:X 2} {:X 3}))
+
+      ;; Multi-goal with comparison.
+      (dl-api-test-set! "multi-goal with comparison"
+        (dl-query
+          (dl-program-data
+            (quote ((n 1) (n 2) (n 3) (n 4) (n 5)))
+            (list))
+          (list (quote (n X)) (list (string->symbol ">") (quote X) 2)))
+        (list {:X 3} {:X 4} {:X 5}))
+
       ;; dl-rule-from-list with no arrow → fact-style.
       (dl-api-test-set! "no arrow → fact-like rule"
         (let