ffi 1.11–1.13: #objc_call inside struct method / protocol / closure / generic

108/108 regression tests pass (+ffi-objc-call-09-in-construct,
+issue-0038 from the prior commit).

One trivial Obj-C call (`[obj hash]` returning NSUInteger) routed
through four sx surface constructs:

  1. struct method body          Probe.fetch
  2. protocol impl method body   impl Hashable for Probe
  3. closure value body          make_hasher
  4. generic function body       hash_through(recv: $T)

No new ABI shapes touched — pins that the `objc_msg_send` lowering
emits identical call shapes regardless of enclosing scope. Each
case validates the result `h_N == h_1` after threading `recv`
appropriately for each context.

The closure path reaches `recv` via a module-level global rather
than capturing the surrounding parameter — issue-0038 (prior
commit) documents the closure free-variable analyzer missing the
`FfiIntrinsicCall` node, with a clean workaround pinned.

tests/expected/ffi-objc-call-09-in-construct.exit

@@ -0,0 +1 @@
+0

tests/expected/ffi-objc-call-09-in-construct.txt

@@ -0,0 +1,4 @@
+fetch != 0   = true
+protocol h2 = true
+closure h3  = true
+generic h4  = true