W14: fix C22/K104 — harness logs IO before invoking the mock (+3 pins)

The interceptor appended the IO-log entry only after the mock returned, so
a throwing mock left no entry and error-path tests falsely reported "never
invoked" through assert-io-called/count (hosts.md C22, core.md K104).

spec/harness.sx make-interceptor now appends {:args :result nil :op}
BEFORE invoking the mock and updates :result in place via dict-set! on
return. This is W14-owned test infrastructure (PLAN.md W14 approach item
4), not a semantics edit.

Pins: suite gate-C22-throwing-mock-logged (throwing mock leaves an entry
with pending result; happy path updates the result; mixed throwing +
successful sequence counts all calls). Harness self-suite (15 tests) and
test-relate-picker (the only other harness consumer) verified green;
285/0 on the pins run.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

spec/tests/test-gate-pins.sx

@@ -217,3 +217,37 @@
         (((fn (c) true) (fn (c) (* c 10))))
         (+ 1 (signal-condition 5)))
       51)))
+
+(defsuite
+  "gate-C22-throwing-mock-logged"
+  (deftest
+    "throwing mock still leaves an IO-log entry"
+    (let
+      ((h (make-harness))
+        (f (make-interceptor h "fetch" (fn (url) (error "boom-io")))))
+      (let
+        ((r (try-call (fn () (f "http://a")))))
+        (assert (not (get r "ok")) "mock error must propagate")
+        (assert-io-called h "fetch")
+        (assert-io-count h "fetch" 1)
+        (assert= (get (io-call-nth h "fetch" 0) "result") nil))))
+  (deftest
+    "successful mock entry gets its result updated in place"
+    (let
+      ((h (make-harness))
+        (f (make-interceptor h "fetch" (fn (url) (str "got:" url)))))
+      (f "http://a")
+      (assert-io-count h "fetch" 1)
+      (assert-io-result h "fetch" 0 "got:http://a")
+      (assert-io-args h "fetch" 0 (list "http://a"))))
+  (deftest
+    "mixed throwing and successful calls are all counted"
+    (let
+      ((h (make-harness))
+        (bomb (make-interceptor h "action" (fn (x) (error "nope"))))
+        (ok-f (make-interceptor h "action" (fn (x) "done"))))
+      (try-call (fn () (bomb 1)))
+      (ok-f 2)
+      (try-call (fn () (bomb 3)))
+      (assert-io-count h "action" 3)
+      (assert= (get (io-call-nth h "action" 1) "result") "done"))))