ios + ir cleanup

- ios: --target ios/ios-sim shorthands, iOS SDK auto-discovery,
  #framework directive + BuildOptions.add_framework hook,
  .app bundle + Info.plist + codesign (ad-hoc and real),
  --codesign-identity/--provisioning-profile/--entitlements flags,
  modules/std/{objc,uikit}.sx, dynamic class registration,
  typed objc_msgSend cast pattern, UIApplicationMain handoff,
  UIWindow scene attach. Runs on iPhone hardware.
- ir: silent .s64 defaults → loud diagnostics,
  resolveReturnType infers from body, sub-byte int sizes match LLVM,
  tuple type interning includes names, compile errors exit 1
- issue-NNNN convention: resolved bugs rename to focused features
- 50 regression tests passing

examples/61-objc-roundtrip.sx

@@ -0,0 +1,28 @@
+// Obj-C runtime FFI smoke test: round-trip a string through NSString.
+//
+// Demonstrates the typed-fn-pointer cast idiom for `objc_msgSend`. Each
+// shape we invoke gets its own variable typed with the exact ABI:
+//
+//   msg_3 : (*void, *void, [*]u8) -> *void = xx objc_msgSend;
+//   msg_2 : (*void, *void) -> [*]u8 = xx objc_msgSend;
+//
+// On ARM64 Apple, objc_msgSend doesn't take a varargs path — invoking it
+// through a typed fn-pointer is the only correct way to land args in the
+// right registers.
+
+#import "modules/std.sx";
+#import "modules/std/objc.sx";
+
+main :: () -> s32 {
+    ns_class      := objc_getClass("NSString".ptr);
+    sel_with_utf8 := sel_registerName("stringWithUTF8String:".ptr);
+    sel_utf8      := sel_registerName("UTF8String".ptr);
+
+    msg_3 : (*void, *void, [*]u8) -> *void = xx objc_msgSend;
+    ns_str := msg_3(ns_class, sel_with_utf8, "hi".ptr);
+
+    msg_2 : (*void, *void) -> [*]u8 = xx objc_msgSend;
+    back := msg_2(ns_str, sel_utf8);
+
+    return xx (back[0] + back[1]); // 'h' + 'i' = 104 + 105 = 209
+}