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_html.lux

@@ -0,0 +1,82 @@
+// Counter with Html Module (Type-safe HTML)
+// Compile with: lux compile examples/web/counter_html.lux --target js -o examples/web/counter_html.js
+//
+// This version uses the Html module for type-safe HTML construction
+// instead of string concatenation. The Html module provides:
+// - Type-safe element constructors (div, button, etc.)
+// - Type-safe attribute constructors (class, onClick, etc.)
+// - Automatic HTML escaping
+
+// ============================================================================
+// 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 - Type-safe HTML using Html module
+// ============================================================================
+
+fn view(model: Model): String = {
+    let count = getCount(model)
+
+    // Build HTML tree using Html module
+    let title = Html.h1([], [Html.text("Lux Counter")])
+    let display = Html.div([Html.class("display")], [Html.text(toString(count))])
+
+    let decBtn = Html.button(
+        [Html.attr("onclick", "dispatch('Decrement')")],
+        [Html.text("-")]
+    )
+    let resetBtn = Html.button(
+        [Html.attr("onclick", "dispatch('Reset')")],
+        [Html.text("Reset")]
+    )
+    let incBtn = Html.button(
+        [Html.attr("onclick", "dispatch('Increment')")],
+        [Html.text("+")]
+    )
+    let buttons = Html.div([Html.class("buttons")], [decBtn, resetBtn, incBtn])
+
+    let container = Html.div([Html.class("counter")], [title, display, buttons])
+
+    // Render to HTML string
+    Html.render(container)
+}
+
+// ============================================================================
+// 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)