mod: Ext 14 — decision wire format for federation transport, 323/323

mod/decision->wire emits a versioned pipe-delimited line (MOD1|r1|hide|spam-hide);
mod/wire->decision parses it back (mod/wire-valid? guards). split-char built over
slice/len (loaded env has no split). Integration test runs the full federated
path: serialize → wire → deserialize → fed-receive-decision trust-gating
(untrusted→advisory, trusted→applied). +16 tests.

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

lib/mod/wire.sx

@@ -0,0 +1,55 @@
+;; lib/mod/wire.sx — portable decision wire format for federation transport.
+;;
+;; fed.sx shares decisions as in-memory dicts and leaves mod/fed-send! as the
+;; transport seam. This is the bytes that cross it: a versioned, pipe-delimited
+;; line encoding the verdict a peer needs (report id, action, rule) — enough to
+;; trust-gate and apply/advise, without shipping the whole proof tree. The
+;; loaded env has no string split, so split is built over slice/len.
+
+(define
+  mod/split-loop
+  (fn
+    (s ch n start pos acc)
+    (if
+      (= pos n)
+      (append acc (list (slice s start n)))
+      (if
+        (= (slice s pos (+ pos 1)) ch)
+        (mod/split-loop
+          s
+          ch
+          n
+          (+ pos 1)
+          (+ pos 1)
+          (append acc (list (slice s start pos))))
+        (mod/split-loop s ch n start (+ pos 1) acc)))))
+
+(define
+  mod/split-char
+  (fn (s ch) (mod/split-loop s ch (len s) 0 0 (list))))
+
+(define
+  mod/decision->wire
+  (fn
+    (d)
+    (str "MOD1|" (get d :report-id) "|" (get d :action) "|" (get d :rule))))
+
+(define
+  mod/wire-valid?
+  (fn
+    (w)
+    (let
+      ((parts (mod/split-char w "|")))
+      (if
+        (= (len parts) 4)
+        (= (nth parts 0) "MOD1")
+        false))))
+
+(define
+  mod/wire->decision
+  (fn
+    (w)
+    (if
+      (mod/wire-valid? w)
+      (let ((parts (mod/split-char w "|"))) {:action (nth parts 2) :wire true :rule (nth parts 3) :report-id (nth parts 1)})
+      nil)))