ffi 2.11 xfail: DSL call site on #jni_class-typed receiver

`act.getWindow()` on `act: *Activity` (where `Activity ::
#jni_class("android/app/Activity") { getWindow :: ... }`) should
lower to `#jni_call(*void)(act, "getWindow", "()Ljava/lang/Object;")`
(omitted-env form picking up env from the enclosing `#jni_env`
scope via 2.16b's lexical-direct path). Today's sema reports
"unresolved: 'getWindow'" because foreign-class members aren't
yet wired into the method-resolution path.

The make-green follow-up needs:
  - sema: register `ForeignClassDecl.members` so method names
    resolve on foreign-class receivers (or suppress the unresolved
    fallback for them).
  - lower: build a `foreign_class_map` in scan pass; new arm in
    `lowerCall`'s method-dispatch site emits a synthetic
    `FfiIntrinsicCall { kind: jni_call, args: [target, "name",
    "(sig)Ret", method_args...] }` with the descriptor derived via
    `jni_descriptor.deriveMethod`.
  - type system: `*Activity` resolution path so `inferExprType`
    on the receiver returns a known type (likely register foreign
    classes as synthetic 0-field structs reusing the struct-type
    machinery).

Larger session needed — pausing here at the xfail.

examples/ffi-jni-class-08-call.sx

@@ -0,0 +1,31 @@
+// Phase 2 step 2.11 (PLAN-FFI.md): xfail then green for DSL call-site
+// lowering — `inst.method(args)` on a `#jni_class`-typed value lowers
+// to `#jni_call(T)(inst, "method", "(sig)Ret", args...)` with the
+// descriptor auto-derived from the sx signature.
+//
+// `#jni_env(env)` brings env into lexical scope; the omitted-env
+// `#jni_call` form (2.16b) picks it up directly.
+
+#import "modules/std.sx";
+
+Activity :: #jni_class("android/app/Activity") {
+    getWindow :: (self: *Self) -> *void;
+}
+
+g_should_call : bool = false;
+
+unused_jni :: (env: *void, act: *Activity) {
+    #jni_env(env) {
+        // Today: this fails — sema doesn't know `Activity` as a type, or
+        // the method dispatch doesn't recognize foreign-class members.
+        win := act.getWindow();
+    }
+}
+
+main :: () -> s32 {
+    if g_should_call {
+        unused_jni(null, null);
+    }
+    print("ok\n");
+    0;
+}

tests/expected/ffi-jni-class-08-call.exit

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

tests/expected/ffi-jni-class-08-call.txt

@@ -0,0 +1 @@
+/Users/agra/projects/sx/examples/ffi-jni-class-08-call.sx:21:16: error: unresolved: 'getWindow'