ffi 1.23: lock in undef shape for #jni_static_call

Test-add for static dispatch — `#jni_static_call(s32)(env, cls,
"max", "(II)I", 3, 7)` exercises GetStaticMethodID + CallStaticIntMethod
plus two integer args. Today the lowering bails on `is_static = true`
with `LLVMGetUndef`. IR snapshot captures the placeholder.

The next commit:
- Adds `Jni.GetStaticMethodID` (113), `Jni.CallStaticVoidMethod` (141),
  `Jni.CallStaticIntMethod` (129), etc. to the constants struct.
- Wires the static path: skip `GetObjectClass` (`target` IS the
  jclass), `NewGlobalRef(target)` to cache it, `GetStaticMethodID`
  for the method, then `CallStatic<Type>Method` per return type.

examples/ffi-jni-call-09-static.sx

@@ -0,0 +1,22 @@
+// Phase 1 step 1.23 (PLAN-FFI.md): `#jni_static_call` lowering.
+// For static dispatch the `target` arg IS already a `jclass`, so the
+// lowering skips `GetObjectClass` and uses `GetStaticMethodID` +
+// `CallStatic<Type>Method` instead. Today `is_static = true` drops
+// to `LLVMGetUndef`; the snapshot captures the placeholder. Next
+// commit wires the static dispatch path.
+
+#import "modules/std.sx";
+
+g_should_call : bool = false;
+
+call_static_max :: (env: *void, cls: *void) -> s32 {
+    #jni_static_call(s32)(env, cls, "max", "(II)I", 3, 7);
+}
+
+main :: () -> s32 {
+    if g_should_call {
+        _ := call_static_max(null, null);
+    }
+    print("ok\n");
+    0;
+}