mod: Ext 11 — batch triage + corpus analytics, 277/277

mod/decide-batch triages a queue; mod/action-histogram summarizes outcomes by
action; mod/rule-coverage + mod/never-fired measure which rules fire across a
corpus — the empirical complement to lint's static unreachable check (lint finds
rules that can't fire; never-fired finds rules that didn't). +17 tests.

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

lib/mod/batch.sx

@@ -0,0 +1,55 @@
+;; lib/mod/batch.sx — batch triage + corpus analytics.
+;;
+;; Operational layer: decide a whole queue of reports at once, summarize the
+;; outcomes by action, and measure which rules actually fire across a corpus.
+;; mod/never-fired is the empirical complement to lint's static unreachable check
+;; (Ext 5): lint finds rules that CAN'T fire by structure; never-fired finds rules
+;; that DIDN'T fire on real data.
+
+(define
+  mod/decide-batch
+  (fn
+    (reports rules)
+    (map (fn (r) (mod/decide-report r reports rules)) reports)))
+
+(define
+  mod/count-action
+  (fn
+    (decisions action)
+    (reduce
+      (fn (acc d) (if (= (get d :action) action) (+ acc 1) acc))
+      0
+      decisions)))
+
+(define mod/action-histogram (fn (decisions) {:keep (mod/count-action decisions "keep") :remove (mod/count-action decisions "remove") :escalate (mod/count-action decisions "escalate") :hide (mod/count-action decisions "hide") :ban (mod/count-action decisions "ban")}))
+
+(define
+  mod/rule-fire-count
+  (fn
+    (decisions rule-name)
+    (reduce
+      (fn (acc d) (if (= (get d :rule) rule-name) (+ acc 1) acc))
+      0
+      decisions)))
+
+(define
+  mod/rule-coverage
+  (fn
+    (reports rules)
+    (let
+      ((decisions (mod/decide-batch reports rules)))
+      (map (fn (rule) {:rule (mod/rule-name rule) :fired (mod/rule-fire-count decisions (mod/rule-name rule))}) rules))))
+
+(define
+  mod/never-fired
+  (fn
+    (reports rules)
+    (reduce
+      (fn
+        (acc c)
+        (if
+          (= (get c :fired) 0)
+          (append acc (list (get c :rule)))
+          acc))
+      (list)
+      (mod/rule-coverage reports rules))))