feat(runtime): native platform backends and UI vessels onto main

ui/examples/native-hello/src/main.el

@@ -0,0 +1,43 @@
+// main.el — Entry point for native-hello.
+//
+// Boot sequence:
+//   1. Initialize the native widget system.
+//   2. Read the manifest.el app{} block for window config.
+//   3. Create the window.
+//   4. Build the widget tree (App.el: app_build).
+//   5. Show the window.
+//   6. Start the run loop (never returns).
+
+import "App.el"
+
+// ── Boot ──────────────────────────────────────────────────────────────────────
+
+native_init()
+
+// Determine the manifest path relative to where we are invoked.
+// When running from the example directory: manifest.el is at ./manifest.el.
+// When invoked from elsewhere: pass EL_MANIFEST env var.
+let manifest_env: String = env("EL_MANIFEST")
+let manifest_path: String = if str_len(manifest_env) > 0 {
+    manifest_env
+} else {
+    "manifest.el"
+}
+
+// Create window from manifest.
+let win: Int = window_from_manifest(manifest_path)
+let g_window = win
+
+if win < 0 {
+    println("Error: failed to create window. Is EL_TARGET_MACOS defined?")
+    exit_program(1)
+}
+
+// Build the widget tree.
+app_build(win)
+
+// Show the window.
+window_show(win)
+
+// Hand control to AppKit. Never returns.
+native_run_loop()