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/59-err-bad-variant.sx

@@ -0,0 +1,22 @@
+// A match arm with a variant name that doesn't exist on the subject's
+// enum/tagged-union produces `error: no variant 'X' on type 'Y'` instead of
+// falling back to the arm index (which used to cause duplicate switch cases
+// and LLVM verification failures).
+
+#import "modules/std.sx";
+
+Shape :: enum {
+    circle: f32;
+    rect: struct { w, h: f32; };
+    none;
+}
+
+main :: () {
+    s :Shape = .circle(3.14);
+    if s == {
+        case .circle: (r) { print("r={}\n", r); }
+        case .Bogus: (x) { print("bogus={}\n", x); }
+        case .none: print("none\n");
+        case .rect: print("rect\n");
+    }
+}