Add TextInput example exposing type system limitations + roadmap

Created a new example that demonstrates what we need for proper string/type support:

**TextInput Example (currently a counter):**
- Initially tried to build reactive text input
- Exposed 5 critical limitations:
  1. String signals stored as i32 (should be i8*)
  2. F-string interpolation incomplete (f"Count: {count}" → "0")
  3. No oninput event (only onclick supported)
  4. No event value passing (can't get input.value)
  5. No string operations (len, concat, etc.)

**Quick Fix Applied:**
- Added type coercion in _emit_signal_globals()
- String signals default to i32 0 (temporary)
- Bool signals convert True/False to 1/0
- Example now uses counter to demonstrate reactive updates

**TYPE_SYSTEM_ROADMAP.md:**
Complete implementation plan for proper type support:
- Phase 1: Type hints extraction (already works!)
- Phase 2: Typed signals (i32, i8*, i1)
- Phase 3: String interpolation in text nodes
- Phase 4: Generalized event system
- Phase 5: Component parameter type checking
- Phase 6: Delegate/callback types

This example will drive the type system implementation. Once complete,
text input will work with proper string signals and reactive updates.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

examples/textinput/TextInput.html

@@ -0,0 +1,123 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Ritz TextInput Example</title>
+    <style>
+        * {
+            margin: 0;
+            padding: 0;
+            box-sizing: border-box;
+        }
+
+        body {
+            font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
+            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+            min-height: 100vh;
+            display: flex;
+            align-items: center;
+            justify-content: center;
+            padding: 20px;
+        }
+
+        .container {
+            background: white;
+            padding: 40px;
+            border-radius: 16px;
+            box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
+            max-width: 500px;
+            width: 100%;
+        }
+
+        h1 {
+            color: #667eea;
+            margin-bottom: 10px;
+            font-size: 32px;
+        }
+
+        .instructions {
+            color: #666;
+            margin-bottom: 30px;
+            font-size: 14px;
+        }
+
+        .button-group {
+            display: flex;
+            align-items: center;
+            gap: 20px;
+            margin: 30px 0;
+        }
+
+        button {
+            width: 60px;
+            height: 60px;
+            font-size: 32px;
+            border: 2px solid #667eea;
+            background: white;
+            color: #667eea;
+            border-radius: 12px;
+            cursor: pointer;
+            transition: all 0.2s;
+            font-weight: bold;
+        }
+
+        button:hover {
+            background: #667eea;
+            color: white;
+            transform: scale(1.1);
+        }
+
+        button:active {
+            transform: scale(0.95);
+        }
+
+        .counter-display {
+            background: #f8f9ff;
+            padding: 20px 40px;
+            border-radius: 12px;
+            border: 3px solid #667eea;
+            font-size: 24px;
+            font-weight: bold;
+            color: #667eea;
+            min-width: 150px;
+            text-align: center;
+        }
+
+        .todo {
+            margin-top: 40px;
+            padding-top: 30px;
+            border-top: 2px dashed #e0e0e0;
+            color: #999;
+            font-size: 14px;
+            font-weight: 600;
+        }
+
+        .todo-list {
+            margin-top: 15px;
+            padding-left: 25px;
+        }
+
+        .todo-list li {
+            color: #666;
+            font-size: 13px;
+            margin: 8px 0;
+            line-height: 1.6;
+        }
+
+        #root {
+            width: 100%;
+        }
+    </style>
+</head>
+<body>
+    <div id="root">Loading...</div>
+
+    <script src="../runtime/ritz-runtime.js"></script>
+    <script>
+        RitzRuntime.loadComponent('TextInput.wasm', 'TextInput', 'root')
+            .then(() => console.log('✅ TextInput loaded'))
+            .catch(err => console.error('❌ Failed to load:', err));
+    </script>
+</body>
+</html>