events: booking lifecycle notifications + 11 tests

booking-notify.sx walks the booking stream into ordered notifications by kind
(booked/promoted/held/confirmed/released/cancelled/waitlisted). Promotion
detected by folding the waitlist (a booking for a waitlisted actor is a
promotion). id=occ-key/seq -> idempotent re-derivation, no double-ping.
Connects ticketing to the delivery layer. 265/265 green.

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

lib/events/tests/booking-notify.sx

@@ -0,0 +1,137 @@
+;; lib/events/tests/booking-notify.sx — lifecycle notifications from the stream.
+
+(define ev-bn-pass 0)
+(define ev-bn-fail 0)
+(define ev-bn-failures (list))
+
+(define
+  ev-bn-check!
+  (fn
+    (name got expected)
+    (if
+      (= got expected)
+      (set! ev-bn-pass (+ ev-bn-pass 1))
+      (do
+        (set! ev-bn-fail (+ ev-bn-fail 1))
+        (append!
+          ev-bn-failures
+          (str name "\n    expected: " expected "\n    got:      " got))))))
+
+(define
+  ev-bn-kinds
+  (fn
+    (notifs)
+    (map (fn (n) (list (get n :recipient) (get n :kind))) notifs)))
+
+(define
+  ev-bn-run-all!
+  (fn
+    ()
+    (do
+      (let
+        ((b (persist/open)))
+        (do
+          (ev/book! b "o" 1 (quote a))
+          (ev/waitlist! b "o" 1 (quote x))
+          (ev/cancel-promote! b "o" 1 (quote a))
+          (let
+            ((ns (ev/booking-notifications b "o" (quote yoga))))
+            (do
+              (ev-bn-check!
+                "lifecycle notifications in order"
+                (ev-bn-kinds ns)
+                (list
+                  (list (quote a) :booked)
+                  (list (quote x) :waitlisted)
+                  (list (quote a) :cancelled)
+                  (list (quote x) :promoted)))
+              (ev-bn-check!
+                "promotion targets the waitlisted actor"
+                (map
+                  (fn (n) (get n :recipient))
+                  (ev/notify-of-kind ns :promoted))
+                (list (quote x)))
+              (ev-bn-check!
+                "a fresh booking is not flagged as a promotion"
+                (len (ev/notify-of-kind ns :booked))
+                1)
+              (ev-bn-check!
+                "every notification carries the event label"
+                (get (first ns) :event)
+                (quote yoga))))))
+      (let
+        ((b (persist/open)))
+        (do
+          (ev/hold! b "p" 3 (quote q))
+          (ev/confirm! b "p" (quote q))
+          (ev-bn-check!
+            "hold then confirm notifications"
+            (ev-bn-kinds (ev/booking-notifications b "p" (quote gig)))
+            (list (list (quote q) :held) (list (quote q) :confirmed)))))
+      (let
+        ((b (persist/open)))
+        (do
+          (ev/hold! b "r" 1 (quote q))
+          (ev/release! b "r" (quote q))
+          (ev-bn-check!
+            "hold then release notifications"
+            (ev-bn-kinds (ev/booking-notifications b "r" (quote gig)))
+            (list (list (quote q) :held) (list (quote q) :released)))))
+      (let
+        ((b (persist/open)))
+        (do
+          (ev/book! b "k" 5 (quote a))
+          (ev/book! b "k" 5 (quote c))
+          (let
+            ((ns (ev/booking-notifications b "k" (quote talk))))
+            (do
+              (ev-bn-check!
+                "notification ids are occ-key/seq"
+                (map (fn (n) (get n :id)) ns)
+                (list "k/1" "k/2"))
+              (ev-bn-check!
+                "re-deriving yields identical ids (idempotent)"
+                (map
+                  (fn (n) (get n :id))
+                  (ev/booking-notifications b "k" (quote talk)))
+                (list "k/1" "k/2"))))))
+      (let
+        ((b (persist/open)))
+        (do
+          (ev/book! b "w" 5 (quote a))
+          (ev-bn-check!
+            "notification projects to (id recipient body)"
+            (ev/booking-notify->msg
+              (first (ev/booking-notifications b "w" (quote talk))))
+            (list
+              "w/1"
+              (quote a)
+              (list :booking-event :booked (quote talk))))))
+      (let
+        ((b (persist/open)))
+        (do
+          (ev/book! b "u" 1 (quote a))
+          (ev/waitlist! b "u" 1 (quote x))
+          (ev/leave-waitlist! b "u" (quote x))
+          (ev-bn-check!
+            "leaving the waitlist emits no notification"
+            (len
+              (ev/notify-of-kind
+                (ev/booking-notifications b "u" (quote e))
+                :left-waitlist))
+            0)
+          (ev-bn-check!
+            "unbooked occurrence has no notifications"
+            (ev/booking-notifications b "empty" (quote e))
+            (list)))))))
+
+(define
+  ev-booking-notify-tests-run!
+  (fn
+    ()
+    (do
+      (set! ev-bn-pass 0)
+      (set! ev-bn-fail 0)
+      (set! ev-bn-failures (list))
+      (ev-bn-run-all!)
+      {:failures ev-bn-failures :total (+ ev-bn-pass ev-bn-fail) :passed ev-bn-pass :failed ev-bn-fail})))