Add :- to op table (prec 1200 xfx); enable assert/asserta/assertz with rule terms

- parser.sx: add (":-" 1200 "xfx") to pl-op-table so (head :- body) parses
  inside paren expressions (parens reset prec to 1200, allowing xfx match)
- parser.sx: extend pl-token-op to accept "op" token type, not just "atom",
  since the tokenizer emits :- as {:type "op" :value ":-"}
- tests/assert_rules.sx: 15 new tests covering assertz/asserta with rule
  terms, conjunction in rule body, recursive rules, and ordering
- conformance.sh: wire in assert_rules suite
- 456 → 471 tests, all passing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/prolog/tests/list_predicates.sx

@@ -53,12 +53,18 @@
 
 (pl-lp-test!
   "==(f(a,b), f(a,b)) succeeds"
-  (pl-solve-once! pl-lp-db (pl-lp-goal "==(f(a,b), f(a,b))" {}) (pl-mk-trail))
+  (pl-solve-once!
+    pl-lp-db
+    (pl-lp-goal "==(f(a,b), f(a,b))" {})
+    (pl-mk-trail))
   true)
 
 (pl-lp-test!
   "==(f(a,b), f(a,c)) fails"
-  (pl-solve-once! pl-lp-db (pl-lp-goal "==(f(a,b), f(a,c))" {}) (pl-mk-trail))
+  (pl-solve-once!
+    pl-lp-db
+    (pl-lp-goal "==(f(a,b), f(a,c))" {})
+    (pl-mk-trail))
   false)
 
 ;; unbound var vs atom: fails (different tags)
@@ -74,7 +80,9 @@
   "==(X, X) succeeds (same runtime var)"
   (pl-solve-once!
     pl-lp-db
-    (pl-instantiate (nth (first (pl-parse "g :- ==(X, X).")) 2) pl-lp-env-same-var)
+    (pl-instantiate
+      (nth (first (pl-parse "g :- ==(X, X).")) 2)
+      pl-lp-env-same-var)
     (pl-mk-trail))
   true)
 
@@ -166,7 +174,10 @@
 
 (pl-lp-test!
   "numlist(5, 3, L) fails (Low > High)"
-  (pl-solve-once! pl-lp-db (pl-lp-goal "numlist(5, 3, L)" {}) (pl-mk-trail))
+  (pl-solve-once!
+    pl-lp-db
+    (pl-lp-goal "numlist(5, 3, L)" {})
+    (pl-mk-trail))
   false)
 
 ;; ── atomic_list_concat/2 ───────────────────────────────────────────
@@ -321,10 +332,4 @@
   (pl-format-term (pl-walk-deep (dict-get pl-lp-env-del3 "R")))
   "[]")
 
-(define pl-list-predicates-tests-run!
-  (fn
-    ()
-    {:failed pl-lp-test-fail
-      :passed pl-lp-test-pass
-      :total pl-lp-test-count
-      :failures pl-lp-test-failures}))
+(define pl-list-predicates-tests-run! (fn () {:failed pl-lp-test-fail :passed pl-lp-test-pass :total pl-lp-test-count :failures pl-lp-test-failures}))