mod: Ext 8 — quorum over distinct reporters (anti-brigade), 232/232

(:reporters-at-least N) compiles to setof(Br, report(_, Br, Sr), Bsr),
length(Bsr, Nr), Nr >= N — counts distinct reporters, not raw reports.
mod/decide-quorum asserts every report's report/3 fact (base engine scopes to the
decided report) so Prolog can aggregate reporters. One user filing 3 reports stays
:keep under quorum while the count rule escalates. Own suite. +9 tests.

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

lib/mod/tests/quorum.sx

@@ -0,0 +1,119 @@
+;; lib/mod/tests/quorum.sx — Ext 8: quorum over distinct reporters.
+
+(define mod-q-count 0)
+(define mod-q-pass 0)
+(define mod-q-fail 0)
+(define mod-q-failures (list))
+
+(define
+  mod-q-test!
+  (fn
+    (name got expected)
+    (begin
+      (set! mod-q-count (+ mod-q-count 1))
+      (if
+        (= got expected)
+        (set! mod-q-pass (+ mod-q-pass 1))
+        (begin
+          (set! mod-q-fail (+ mod-q-fail 1))
+          (append!
+            mod-q-failures
+            (str name "\n    expected: " expected "\n    got:      " got)))))))
+
+(define
+  mod-q-rules
+  (list
+    (mod/mk-rule
+      "quorum-hide"
+      :hide (list (list :reporters-at-least 2)))
+    (mod/mk-rule "default-keep" :keep (list))))
+
+;; ── two distinct reporters meet quorum ──
+
+(define
+  mod-q-two
+  (list
+    (mod/mk-report "r1" "alice" "bob" "off-topic")
+    (mod/mk-report "r2" "carol" "bob" "off-topic")))
+
+(mod-q-test!
+  "two distinct reporters → hide"
+  (get (mod/decide-quorum (first mod-q-two) mod-q-two mod-q-rules) :action)
+  "hide")
+(mod-q-test!
+  "quorum decision names the rule"
+  (get (mod/decide-quorum (first mod-q-two) mod-q-two mod-q-rules) :rule)
+  "quorum-hide")
+(mod-q-test!
+  "quorum decision tagged strategy"
+  (get (mod/decide-quorum (first mod-q-two) mod-q-two mod-q-rules) :strategy)
+  "quorum")
+
+;; ── single reporter does not meet quorum ──
+
+(define mod-q-one (list (mod/mk-report "r1" "alice" "bob" "off-topic")))
+(mod-q-test!
+  "one reporter → keep (below quorum)"
+  (get (mod/decide-quorum (first mod-q-one) mod-q-one mod-q-rules) :action)
+  "keep")
+
+;; ── anti-brigade: one user filing many reports does NOT meet quorum ──
+
+(define
+  mod-q-brigade
+  (list
+    (mod/mk-report "r1" "alice" "bob" "off-topic")
+    (mod/mk-report "r2" "alice" "bob" "off-topic")
+    (mod/mk-report "r3" "alice" "bob" "off-topic")))
+
+(mod-q-test!
+  "three reports, one reporter → keep (quorum counts distinct)"
+  (get
+    (mod/decide-quorum (first mod-q-brigade) mod-q-brigade mod-q-rules)
+    :action)
+  "keep")
+
+;; contrast: the count rule WOULD fire on the same brigade (3 reports ≥ 3) —
+;; quorum is strictly stronger against single-actor brigading
+(mod-q-test!
+  "count rule fires on the brigade (distinct from quorum)"
+  (get
+    (mod/decide-report (first mod-q-brigade) mod-q-brigade mod/default-rules)
+    :action)
+  "escalate")
+
+;; ── three distinct reporters ──
+
+(define
+  mod-q-three
+  (list
+    (mod/mk-report "r1" "alice" "bob" "off-topic")
+    (mod/mk-report "r2" "carol" "bob" "off-topic")
+    (mod/mk-report "r3" "dave" "bob" "off-topic")))
+
+(mod-q-test!
+  "three distinct reporters → hide"
+  (get
+    (mod/decide-quorum (first mod-q-three) mod-q-three mod-q-rules)
+    :action)
+  "hide")
+(mod-q-test!
+  "quorum proof goal solved"
+  (get
+    (first
+      (get
+        (get
+          (mod/decide-quorum (first mod-q-three) mod-q-three mod-q-rules)
+          :proof)
+        :goals))
+    :solved)
+  true)
+
+;; ── cond->goal compiles :reporters-at-least ──
+
+(mod-q-test!
+  "cond->goal :reporters-at-least"
+  (mod/cond->goal (list :reporters-at-least 2) "Id")
+  "report(Id, _, Sr), setof(Br, report(_, Br, Sr), Bsr), length(Bsr, Nr), Nr >= 2")
+
+(define mod-quorum-tests-run! (fn () {:failures mod-q-failures :total mod-q-count :passed mod-q-pass :failed mod-q-fail}))