events: end-to-end delivery pipeline (derivation -> notify flow) + 8 tests

ev/deliver-messages bridges SX notification messages to the Scheme notify
flow: each (id recipient body) is serialized to s-expr text, spliced as quoted
data into the digest-flow program, delivered over an injected transport, and
results unboxed. Integration suite drives all three derivations (reminders /
booking-notify / reschedule) through delivery end to end; empty batch guarded
(empty digest completes without suspending). 303/303 green.

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

lib/events/notify.sx

@@ -36,3 +36,62 @@
 (define
   ev/notify-run
   (fn (prog) (flow-run (str ev-notify-flows-src "\n" prog))))
+
+;; ---- end-to-end delivery: SX messages -> the notify flow ----
+;; Bridges the SX notification-derivation modules (reminders / booking-notify /
+;; reschedule) to the durable delivery flow. An SX message (id recipient body)
+;; is serialized to s-expression text and spliced into the Scheme program as
+;; quoted data, then the digest flow delivers the batch over an injected
+;; transport. Strings round-trip through the guest Scheme as {:scm-string ...}
+;; boxes; results are unboxed back to plain SX.
+
+;; A default transport (Scheme source): always reports delivered.
+(define ev-notify-ok-transport "(lambda (k p) (list (quote ok) (quote sent)))")
+
+(define
+  ev-notify-join
+  (fn
+    (parts sep)
+    (if
+      (empty? parts)
+      ""
+      (reduce (fn (acc p) (str acc sep p)) (first parts) (rest parts)))))
+
+(define ev-msg->quoted (fn (m) (str "(quote " (serialize m) ")")))
+
+(define
+  ev-msgs->scheme
+  (fn
+    (msgs)
+    (str "(list " (ev-notify-join (map ev-msg->quoted msgs) " ") ")")))
+
+(define
+  ev-unbox-str
+  (fn
+    (x)
+    (if (and (dict? x) (has-key? x :scm-string)) (get x :scm-string) x)))
+
+(define
+  ev-unbox-result
+  (fn (r) (map (fn (item) (map ev-unbox-str item)) r)))
+
+;; Deliver a list of SX messages through the digest flow over `transport-src`
+;; (a Scheme (kind payload) -> (ok ..)|(retry reason) lambda source). `maxn`
+;; bounds retries per message, `maxticks` bounds host service ticks. Returns the
+;; per-message outcomes unboxed: (("delivered"|"failed" <id> <n-or-reason>) ...)
+(define
+  ev/deliver-messages
+  (fn
+    (msgs transport-src maxn maxticks)
+    (ev-unbox-result
+      (ev/notify-run
+        (str
+          "(define msgs "
+          (ev-msgs->scheme msgs)
+          ") (if (null? msgs) (list) (let ((s (flow/start (ev-deliver-digest "
+          maxn
+          ") msgs))) (begin (flow-run-host "
+          transport-src
+          " "
+          maxticks
+          ") (flow/result (car (cdr s))))))")))))