feat(ui): native vessel, HTML vessel update, native hello examples, profile card, UI tools

el-native vessel: El-level wrappers around __widget_* C builtins, exposing
vstack, label, button, text_field, etc. as clean El functions for application code.

el-html/main.elh: updated extern declarations for the HTML vessel's codegen API.

native-hello: cross-platform desktop example (AppKit/GTK4/Win32/SDL2) with
build scripts, Dockerfiles for Linux/Pi, and Win32 cross-compile support.

native-hello-android: Gradle project with ElBridge integration and build script.

native-hello-ios: Xcode project for the iOS UIKit target.

profile-card: manifest.el for a styling/layout/i18n example app that exercises
el-style, el-layout, el-i18n, el-config, and el-secrets vessels.

ui/tools/native-codegen: Python codegen pass (el_ui_native_codegen.py) that
lowers el-ui component DSL to el-native vessel calls, plus build script and
test fixtures.

ui/examples/native-hello-android/app/src/main/res/layout/activity_main.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  activity_main.xml — placeholder layout.
+
+  The el program sets the content view programmatically via ElBridge.setContentView
+  (called from __window_show → el_android_window_show). This layout is not used
+  at runtime but satisfies Gradle's res/ validation checks.
+-->
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical" />

ui/examples/native-hello-android/app/src/main/res/values/strings.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="app_name">el-native</string>
+</resources>