feat: add stdlib and browser examples

- stdlib/html.lux: Type-safe HTML construction
- stdlib/browser.lux: Browser utilities
- examples/web/: Counter app with DOM manipulation
- examples/counter.lux: Simple counter example

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

examples/web/counter.lux

@@ -0,0 +1,62 @@
+// Simple Counter for Browser
+// Compile with: lux compile examples/web/counter.lux --target js -o examples/web/counter.js
+
+// ============================================================================
+// Model
+// ============================================================================
+
+type Model = | Counter(Int)
+
+fn getCount(m: Model): Int = match m { Counter(n) => n }
+
+fn init(): Model = Counter(0)
+
+// ============================================================================
+// Messages
+// ============================================================================
+
+type Msg = | Increment | Decrement | Reset
+
+// ============================================================================
+// Update
+// ============================================================================
+
+fn update(model: Model, msg: Msg): Model =
+    match msg {
+        Increment => Counter(getCount(model) + 1),
+        Decrement => Counter(getCount(model) - 1),
+        Reset => Counter(0)
+    }
+
+// ============================================================================
+// View - Returns HTML string for simplicity
+// ============================================================================
+
+fn view(model: Model): String = {
+    let count = getCount(model)
+    "<div class=\"counter\">" +
+        "<h1>Lux Counter</h1>" +
+        "<div class=\"display\">" + toString(count) + "</div>" +
+        "<div class=\"buttons\">" +
+            "<button onclick=\"dispatch('Decrement')\">-</button>" +
+            "<button onclick=\"dispatch('Reset')\">Reset</button>" +
+            "<button onclick=\"dispatch('Increment')\">+</button>" +
+        "</div>" +
+    "</div>"
+}
+
+// ============================================================================
+// Export for browser runtime
+// ============================================================================
+
+fn luxInit(): Model = init()
+
+fn luxUpdate(model: Model, msgName: String): Model =
+    match msgName {
+        "Increment" => update(model, Increment),
+        "Decrement" => update(model, Decrement),
+        "Reset" => update(model, Reset),
+        _ => model
+    }
+
+fn luxView(model: Model): String = view(model)