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/build-gtk4/.vessel_keep.txt

@@ -0,0 +1,55 @@
+_button
+_color_hex_a
+_color_hex_b
+_color_hex_g
+_color_hex_r
+_hex_channel
+_hex_nibble
+_hstack
+_image
+_label
+_manifest_height
+_manifest_min_height
+_manifest_min_width
+_manifest_read
+_manifest_title
+_manifest_width
+_native_init
+_native_run_loop
+_scroll
+_style_button_primary
+_style_label_body
+_style_label_heading
+_style_label_muted
+_style_surface
+_text_area
+_text_field
+_vstack
+_vstack_tight
+_widget_add_child
+_widget_destroy
+_widget_get_text
+_widget_on_change
+_widget_on_click
+_widget_on_submit
+_widget_remove_child
+_widget_set_bg_color
+_widget_set_bg_color_hex
+_widget_set_color
+_widget_set_color_hex
+_widget_set_corner_radius
+_widget_set_disabled
+_widget_set_flex
+_widget_set_font
+_widget_set_height
+_widget_set_hidden
+_widget_set_padding
+_widget_set_padding_all
+_widget_set_padding_xy
+_widget_set_text
+_widget_set_width
+_window_create
+_window_from_manifest
+_window_set_title
+_window_show
+_zstack