mod: Ext 13 — SLA sweep over pending lifecycle cases, 307/307

Composes lifecycle (Phase 3) with time (Ext 12): a timed-case pairs a case with
its state-entry tick; mod/overdue? flags pending cases (open/triaged/appealed)
past a deadline; mod/sla-sweep returns the breached report ids. Terminal states
never breach. Pure overlay — lifecycle stays timeless, caller stamps entry. +15 tests.

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

lib/mod/sla.sx

@@ -0,0 +1,47 @@
+;; lib/mod/sla.sx — service-level sweep over pending lifecycle cases.
+;;
+;; Composes the Phase-3 lifecycle with the Ext-12 time dimension: a case left in a
+;; pending state (open / triaged / appealed) past a deadline has breached SLA and
+;; should resurface. A timed-case pairs a case with the tick it entered its
+;; current state (the caller stamps this — the lifecycle stays timeless and pure).
+;; Terminal states (decided / final) never breach.
+
+(define mod/pending-states (list "open" "triaged" "appealed"))
+(define mod/pending-state? (fn (s) (mod/member? s mod/pending-states)))
+
+(define mod/mk-timed-case (fn (c entered-at) {:entered-at entered-at :case c}))
+(define mod/tc-case (fn (tc) (get tc :case)))
+(define mod/tc-entered-at (fn (tc) (get tc :entered-at)))
+
+(define
+  mod/overdue?
+  (fn
+    (tc now deadline)
+    (if
+      (mod/pending-state? (mod/case-state (mod/tc-case tc)))
+      (< deadline (- now (mod/tc-entered-at tc)))
+      false)))
+
+(define
+  mod/sla-sweep
+  (fn
+    (timed-cases now deadline)
+    (reduce
+      (fn
+        (acc tc)
+        (if
+          (mod/overdue? tc now deadline)
+          (append
+            acc
+            (list (mod/report-id (mod/case-report (mod/tc-case tc)))))
+          acc))
+      (list)
+      timed-cases)))
+
+(define
+  mod/overdue-count
+  (fn
+    (timed-cases now deadline)
+    (len (mod/sla-sweep timed-cases now deadline))))
+
+(define mod/age (fn (tc now) (- now (mod/tc-entered-at tc))))