events: injected federation transport (fed-sx-ready) + 6 tests

fetch abstracts how a peer's agenda arrives: (fetch peer-id ws we) ->
{:status :ok :occurrences} | {:status :error}. ev/federated-agenda-via merges
local + trusted peers fetched via the transport; unreachable peers degrade
gracefully. ev/peer-fetch = in-process adapter; ev/federation-status reports
reachability. A real fed-sx transport drops in unchanged. 278/278 green.

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

lib/events/tests/federation.sx

@@ -218,6 +218,63 @@
             (ev/federated-free? local-db peers (list (quote berlin)) (quote nia) (ev-dt 2026 6 1 15 0) (ev-dt 2026 6 1 16 0))
             true))))))
 
+;; ---- injected transport (fed-sx) ----
+(define
+  ev-fd-tx-run-all!
+  (fn
+    ()
+    (let
+      ((local (ev/schedule (ev/empty) (quote yoga) (ev-dt 2026 6 1 9 0) 60 nil 20))
+        (berlin (ev/peer (quote berlin) (ev/schedule (ev/empty) (quote meetup) (ev-dt 2026 6 1 12 0) 90 nil 100)))
+        (ws (ev-date 2026 6 1))
+        (we (ev-date 2026 6 2)))
+      (let
+        ((fetch (ev/peer-fetch (list berlin))))
+        (do
+          ;; in-process adapter merges through the transport interface
+          (ev-fd-check!
+            "federated-agenda-via merges local + fetched peer"
+            (map (fn (o) (list (get o :origin) (get o :id)))
+              (ev/federated-agenda-via local (list (quote berlin)) ws we fetch))
+            (list (list :local (quote yoga)) (list (quote berlin) (quote meetup))))
+          ;; an unreachable / unknown peer degrades gracefully
+          (ev-fd-check!
+            "an unreachable peer is skipped, agenda still served"
+            (map (fn (o) (get o :origin))
+              (ev/federated-agenda-via local (list (quote berlin) (quote ghost)) ws we fetch))
+            (list :local (quote berlin)))
+          ;; reachability report
+          (ev-fd-check!
+            "federation-status reports per-peer reachability"
+            (ev/federation-status (list (quote berlin) (quote ghost)) ws we fetch)
+            (list (list (quote berlin) :ok) (list (quote ghost) :error)))
+          ;; an explicit remote transport (returns occurrences directly)
+          (let
+            ((remote-fetch
+               (fn
+                 (pid rws rwe)
+                 (if (= pid (quote tokyo))
+                   {:status :ok
+                     :occurrences (list (ev-occ (quote standup) (ev-dt 2026 6 1 8 0) 15))}
+                   {:status :error :reason :unreachable}))))
+            (do
+              (ev-fd-check!
+                "a remote transport's occurrences merge with origin tags"
+                (map (fn (o) (list (get o :origin) (get o :id)))
+                  (ev/federated-agenda-via local (list (quote tokyo)) ws we remote-fetch))
+                (list (list (quote tokyo) (quote standup)) (list :local (quote yoga))))
+              (ev-fd-check!
+                "remote transport error degrades to local only"
+                (map (fn (o) (get o :origin))
+                  (ev/federated-agenda-via local (list (quote osaka)) ws we remote-fetch))
+                (list :local))))
+          ;; no trusted peers -> only local
+          (ev-fd-check!
+            "no trusted peer ids yields only local"
+            (map (fn (o) (get o :origin))
+              (ev/federated-agenda-via local (list) ws we fetch))
+            (list :local)))))))
+
 (define
   ev-federation-tests-run!
   (fn
@@ -228,4 +285,5 @@
       (set! ev-fd-failures (list))
       (ev-fd-run-all!)
       (ev-fd-fb-run-all!)
+      (ev-fd-tx-run-all!)
       {:failures ev-fd-failures :total (+ ev-fd-pass ev-fd-fail) :passed ev-fd-pass :failed ev-fd-fail})))