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

ui/examples/native-hello/manifest.el

@@ -0,0 +1,19 @@
+package "native-hello" {
+    version "0.1.0"
+    description "Minimal native UI test for the el native widget system."
+    authors ["Neuron Technologies"]
+    edition "2026"
+}
+
+build {
+    entry "src/main.el"
+    target "debug"
+}
+
+app {
+    window_title "Hello from el-native"
+    window_width 480
+    window_height 320
+    min_width 360
+    min_height 240
+}