add native window/webview builtins to el runtime

Adds five new builtins backed by wry 0.47 + tao 0.30:
- window_open(title, width, height) — configure window
- webview_load_url(url) — set URL to navigate to
- webview_load_html(html) — set HTML to display
- webview_eval(js) — queue JS to eval after load
- window_run() — open native OS window and run event loop (blocking, exits on close)

WebViewState is stored in a thread_local. window_run() calls
tao's event_loop.run() which never returns; process exits when
the window is closed via std::process::exit(0).

bin/el/Cargo.toml

@@ -34,3 +34,5 @@ hmac        = { workspace = true }
 sha2        = { workspace = true }
 hex         = { workspace = true }
 base64      = { workspace = true }
+wry         = "0.47"
+tao         = "0.30"

bin/el/src/main.rs

@@ -56,6 +56,29 @@ thread_local! {
         std::cell::RefCell::new(None);
 }
 
+// ── Native window / WebView state ────────────────────────────────────────────
+
+#[derive(Default)]
+struct WebViewState {
+    title: String,
+    width: u32,
+    height: u32,
+    url: Option<String>,
+    html: Option<String>,
+    pending_js: Vec<String>,
+}
+
+thread_local! {
+    static WV_STATE: std::cell::RefCell<WebViewState> = std::cell::RefCell::new(WebViewState {
+        title: "Neuron".to_string(),
+        width: 1200,
+        height: 800,
+        url: None,
+        html: None,
+        pending_js: Vec::new(),
+    });
+}
+
 // ── CLI definition ────────────────────────────────────────────────────────────
 
 #[derive(Parser, Debug)]
@@ -4163,6 +4186,82 @@ fn dispatch_builtin(
             BuiltinResult::Handled
         }
 
+        // ── Native window / WebView builtins ──────────────────────────────────
+
+        "window_open" => {
+            // window_open(title: String, width: Int, height: Int) -> Void
+            let height = match stack.pop().unwrap_or(Value::Nil) { Value::Int(n) => n as u32, _ => 800 };
+            let width  = match stack.pop().unwrap_or(Value::Nil) { Value::Int(n) => n as u32, _ => 1200 };
+            let title  = match stack.pop().unwrap_or(Value::Nil) { Value::Str(s) => s, _ => "Neuron".to_string() };
+            WV_STATE.with(|st| {
+                let mut s = st.borrow_mut();
+                s.title  = title;
+                s.width  = width;
+                s.height = height;
+            });
+            BuiltinResult::Handled
+        }
+
+        "webview_load_url" => {
+            // webview_load_url(url: String) -> Void
+            let url = match stack.pop().unwrap_or(Value::Nil) { Value::Str(s) => s, _ => { return BuiltinResult::Handled; } };
+            WV_STATE.with(|st| st.borrow_mut().url = Some(url));
+            BuiltinResult::Handled
+        }
+
+        "webview_load_html" => {
+            // webview_load_html(html: String) -> Void
+            let html = match stack.pop().unwrap_or(Value::Nil) { Value::Str(s) => s, _ => { return BuiltinResult::Handled; } };
+            WV_STATE.with(|st| st.borrow_mut().html = Some(html));
+            BuiltinResult::Handled
+        }
+
+        "webview_eval" => {
+            // webview_eval(js: String) -> Void
+            let js = match stack.pop().unwrap_or(Value::Nil) { Value::Str(s) => s, _ => { return BuiltinResult::Handled; } };
+            WV_STATE.with(|st| st.borrow_mut().pending_js.push(js));
+            BuiltinResult::Handled
+        }
+
+        "window_run" => {
+            // window_run() -> Void (never returns; exits process on window close)
+            use tao::event::{Event, WindowEvent};
+            use tao::event_loop::{ControlFlow, EventLoop};
+            use tao::window::WindowBuilder;
+            use wry::WebViewBuilder;
+
+            let (title, width, height, url, html) = WV_STATE.with(|st| {
+                let s = st.borrow();
+                (s.title.clone(), s.width, s.height, s.url.clone(), s.html.clone())
+            });
+
+            let event_loop = EventLoop::new();
+            let window = WindowBuilder::new()
+                .with_title(title)
+                .with_inner_size(tao::dpi::LogicalSize::new(width, height))
+                .build(&event_loop)
+                .expect("failed to create window");
+
+            let mut builder = WebViewBuilder::new();
+            if let Some(u) = url {
+                builder = builder.with_url(u);
+            } else if let Some(h) = html {
+                builder = builder.with_html(h);
+            } else {
+                builder = builder.with_html("<h1>Neuron</h1>");
+            }
+
+            let _webview = builder.build(&window).expect("failed to create webview");
+
+            // event_loop.run() never returns (diverging fn `-> !`)
+            event_loop.run(move |event, _, control_flow| {
+                *control_flow = ControlFlow::Wait;
+                if let Event::WindowEvent { event: WindowEvent::CloseRequested, .. } = event {
+                    std::process::exit(0);
+                }
+            });
+        }
+
         _ => BuiltinResult::NotBuiltin,
     }
 }

crates/el-types/src/types.rs

@@ -262,6 +262,13 @@ impl TypeEnv {
         env.functions.insert("cursor_col".into(), str_fn(vec![i.clone()], Type::Void));
         env.functions.insert("http_sse_post".into(), str_fn(vec![s.clone(), s.clone(), s.clone()], s.clone()));
 
+        // Native window / WebView builtins
+        env.functions.insert("window_open".into(),      str_fn(vec![s.clone(), i.clone(), i.clone()], Type::Void));
+        env.functions.insert("webview_load_url".into(), str_fn(vec![s.clone()], Type::Void));
+        env.functions.insert("webview_load_html".into(), str_fn(vec![s.clone()], Type::Void));
+        env.functions.insert("webview_eval".into(),     str_fn(vec![s.clone()], Type::Void));
+        env.functions.insert("window_run".into(),       str_fn(vec![], Type::Void));
+
         // Math
         for name in &["math_abs","math_floor","math_ceil","math_round","math_sqrt"] {
             env.functions.insert(name.to_string(), str_fn(vec![u.clone()], u.clone()));