test: migrate examples to XXXX-category-name layout + split expected streams

Rename all example tests/companions to the XXXX-category-test-name scheme
(per-category 100-blocks: basic 0010, types 0100, ... errors 1000,
diagnostics 1100, ffi 1200, ffi-objc 1300, ffi-jni 1400, vectors 1500,
platform 1600). Companions and dir/C fixtures move in lockstep with their
parent test; #import/#source/#include paths rewritten to match.

Expected output now lives in examples/expected/ (a sibling dir of the
tests) split into three streams per the new convention:
  <name>.exit / <name>.stdout / <name>.stderr  (+ optional <name>.ir)

run_examples.sh rewritten: scans examples/ and issues/ for an
expected/<name>.exit marker, captures stdout and stderr separately (no
more 2>&1), compares each stream + exit + optional IR snapshot.

Behavior validated unchanged: every renamed test reproduces its prior
merged output + exit (diffs limited to file paths/basenames embedded in
diagnostics + traces, which correctly reflect the new names). Suite:
292 passed, 0 failed. 50-smoke.sx split + issue relocation + docs follow
in subsequent commits.

examples/1608-platform-uikit-window.sx

@@ -0,0 +1,94 @@
+// Show something on screen — a UIWindow with a colored UIViewController root.
+//
+// Builds on 5.7's AppDelegate. Inside `didFinishLaunching`, we:
+//   1. [[UIWindow alloc] initWithFrame:CGRect]
+//   2. [[UIViewController alloc] init]; set view.backgroundColor
+//   3. window.rootViewController = vc
+//   4. [window makeKeyAndVisible]
+//
+// We hardcode the frame to 1024×1024 to avoid the struct-return ABI of
+// `[UIScreen mainScreen].bounds` for now — any frame bigger than the device
+// covers the screen, modulo safe-area insets.
+//
+// `g_window` is a module-level global so the window outlives the IMP scope
+// (no ARC; UIKit retains it as the key window anyway).
+
+#import "modules/std.sx";
+#import "modules/std/uikit.sx";
+
+g_window : *void = ---;
+
+// AppDelegate's `window` property. iOS queries this getter to discover the
+// app's key window; without it, the legacy code path creates its own empty
+// window and ignores anything we configure.
+window_getter :: (self: *void, _cmd: *void) -> *void callconv(.c) {
+    return g_window;
+}
+window_setter :: (self: *void, _cmd: *void, w: *void) callconv(.c) {
+    g_window = w;
+}
+
+did_finish_launching :: (self: *void, _cmd: *void, app: *void, opts: *void) -> u8 callconv(.c) {
+    UIWindow         := objc_getClass("UIWindow".ptr);
+    UIViewController := objc_getClass("UIViewController".ptr);
+    UIColor          := objc_getClass("UIColor".ptr);
+
+    sel_alloc            := sel_registerName("alloc".ptr);
+    sel_init             := sel_registerName("init".ptr);
+    sel_init_with_scene  := sel_registerName("initWithWindowScene:".ptr);
+    sel_view             := sel_registerName("view".ptr);
+    sel_system_blue      := sel_registerName("systemBlueColor".ptr);
+    sel_set_bg           := sel_registerName("setBackgroundColor:".ptr);
+    sel_set_root_vc      := sel_registerName("setRootViewController:".ptr);
+    sel_make_key_visible := sel_registerName("makeKeyAndVisible".ptr);
+    sel_connected_scenes := sel_registerName("connectedScenes".ptr);
+    sel_any_object       := sel_registerName("anyObject".ptr);
+
+    msg_o   : (*void, *void)               -> *void = xx objc_msgSend;
+    msg_v   : (*void, *void)               -> void  = xx objc_msgSend;
+    msg_oo  : (*void, *void, *void)        -> void  = xx objc_msgSend;
+    msg_ooo : (*void, *void, *void)        -> *void = xx objc_msgSend;
+
+    // Modern iOS path: get the connected windowScene, then construct the
+    // window via initWithWindowScene: so UIKit auto-sizes it and attaches
+    // it to the display in one step.
+    scenes := msg_o(app, sel_connected_scenes);
+    scene  := msg_o(scenes, sel_any_object);
+    if scene == xx 0 { NSLog(ns_string("[sx] scene NULL\n".ptr)); return 1; }
+    NSLog(ns_string("[sx] scene: ok\n".ptr));
+
+    win_raw := msg_o(UIWindow, sel_alloc);
+    g_window = msg_ooo(win_raw, sel_init_with_scene, scene);
+    NSLog(ns_string("[sx] window: ok\n".ptr));
+
+    vc_raw := msg_o(UIViewController, sel_alloc);
+    vc     := msg_o(vc_raw, sel_init);
+    msg_oo(g_window, sel_set_root_vc, vc);
+
+    blue := msg_o(UIColor, sel_system_blue);
+    view := msg_o(vc, sel_view);
+    msg_oo(view, sel_set_bg, blue);
+    msg_oo(g_window, sel_set_bg, blue);
+
+    msg_v(g_window, sel_make_key_visible);
+    NSLog(ns_string("[sx] makeKeyAndVisible done\n".ptr));
+    return 1;
+}
+
+main :: () -> s32 {
+    UIResponder := objc_getClass("UIResponder".ptr);
+    SxAppDelegate := objc_allocateClassPair(UIResponder, "SxAppDelegate".ptr, 0);
+
+    class_addMethod(SxAppDelegate,
+        sel_registerName("application:didFinishLaunchingWithOptions:".ptr),
+        xx did_finish_launching, "c@:@@".ptr);
+    class_addMethod(SxAppDelegate,
+        sel_registerName("window".ptr),
+        xx window_getter, "@@:".ptr);
+    class_addMethod(SxAppDelegate,
+        sel_registerName("setWindow:".ptr),
+        xx window_setter, "v@:@".ptr);
+
+    objc_registerClassPair(SxAppDelegate);
+    return UIApplicationMain(0, xx 0, xx 0, ns_string("SxAppDelegate".ptr));
+}