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/scoreboard.md

@@ -1,6 +1,6 @@
 # datalog scoreboard
 
-**165 / 165 passing** (0 failure(s)).
+**167 / 167 passing** (0 failure(s)).
 
 | Suite | Passed | Total | Status |
 |-------|--------|-------|--------|
@@ -12,5 +12,5 @@
 | semi_naive | 8 | 8 | ok |
 | negation | 10 | 10 | ok |
 | aggregates | 16 | 16 | ok |
-| api | 9 | 9 | ok |
+| api | 11 | 11 | ok |
 | demo | 13 | 13 | ok |