ffi 1.0: xfail parser test for #objc_call(T)(recv, "sel:", args...)

98/98 regression tests pass (+ffi-objc-call-01-parse with xfail
snapshot capturing today's parse error).

Phase 1 of PLAN-FFI.md introduces three compiler intrinsics
(`#objc_call`, `#jni_call`, `#jni_static_call`) that lift the
ceremony off the existing typed-`objc_msgSend` and JNI dispatch
patterns. This is the first step of the cadence:

  1.0 (this commit): test-add. Locks the current parse rejection.
  1.1 (next):        make-green. Parser accepts the new syntax;
                     this snapshot updates to whatever the next
                     pipeline stage produces (sema/codegen still
                     can't lower the intrinsic — that's later
                     phase-1 steps).
  1.3+:              codegen lands; the test eventually runs
                     cleanly against Foundation.

`inline if false` wraps the call site so the AST carries the node
but no codegen runs for it. Lets Phase 1.1's parse-only test pass
without dragging in the sema/codegen plumbing prematurely.

examples/ffi-objc-call-01-parse.sx

@@ -0,0 +1,25 @@
+// Phase 1 step 1.0 (PLAN-FFI.md): xfail test for the `#objc_call`
+// parser. The shape is `#objc_call(ReturnT)(receiver, "selector:",
+// args...)` — return type in the first parens, then a normal call.
+// Today the parser rejects this; the snapshot captures the rejection.
+//
+// Phase 1.1 adds the parse rule and the snapshot updates to whatever
+// the next pipeline stage produces (sema / codegen can't lower the
+// intrinsic until later steps).
+//
+// Phase 1.3+ wires the lowering (selector interning + objc_msgSend
+// dispatch) and the test eventually runs cleanly against Foundation.
+
+#import "modules/std.sx";
+
+main :: () -> s32 {
+    // `#objc_call(void)` with a null receiver — never executed (this
+    // file's purpose is parser surface coverage). `inline if false`
+    // would suppress sema/codegen too, but for the parse-only step
+    // we want the AST to actually carry the node.
+    inline if false {
+        #objc_call(void)(null, "init");
+    }
+    print("parse-only ok\n");
+    0;
+}

tests/expected/ffi-objc-call-01-parse.exit

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

tests/expected/ffi-objc-call-01-parse.txt

@@ -0,0 +1 @@
+/Users/agra/projects/sx/examples/ffi-objc-call-01-parse.sx:21:9: error: unexpected token in expression