mod: Phase 1 — report schema + policy engine on Prolog, 31/31

Reports → Prolog facts (report/3, classification/2, report_count/2); ordered
policy rules compile to policy_action/3 clauses, first match wins via
pl-query-one. Decisions carry their proof (matching rule + conditions +
evidence). Spam/abuse keyword classification, repeated-report escalation via
Prolog join+arithmetic, no-rule→keep default. Registry api + conformance harness.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/mod/api.sx

@@ -0,0 +1,44 @@
+;; lib/mod/api.sx — report registry + public entry points.
+;;
+;; mod/report files a report (assigning a sequential id) into the in-memory
+;; registry; mod/decide resolves an id and runs the policy engine against the
+;; current registry and rule set.
+
+(define mod/*reports* (list))
+(define mod/*counter* 0)
+(define mod/*rules* mod/default-rules)
+
+(define
+  mod/reset!
+  (fn
+    ()
+    (begin (set! mod/*reports* (list)) (set! mod/*counter* 0))))
+
+(define
+  mod/report
+  (fn
+    (by about reason)
+    (begin
+      (set! mod/*counter* (+ mod/*counter* 1))
+      (let
+        ((id (str "r" mod/*counter*)))
+        (let
+          ((r (mod/mk-report id by about reason)))
+          (begin (append! mod/*reports* r) r))))))
+
+(define
+  mod/get-report
+  (fn
+    (id)
+    (reduce
+      (fn (acc r) (if (= (mod/report-id r) id) r acc))
+      nil
+      mod/*reports*)))
+
+(define
+  mod/decide
+  (fn
+    (id)
+    (let
+      ((r (mod/get-report id)))
+      (if (nil? r) nil (mod/decide-report r mod/*reports* mod/*rules*)))))