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.py

@@ -0,0 +1,60 @@
+"""
+TextInput example - Reactive counter to demonstrate what we need for text input.
+
+Current limitations exposed by this example:
+1. No oninput event (only onclick) - need generalized event handling
+2. No string signals (only i32) - need type system
+3. No f-string interpolation with signals in text nodes
+4. No event value passing (onclick doesn't pass event data)
+5. No string operations (len, concat, etc.)
+
+For now, using a counter to demonstrate the reactive infrastructure
+that text input will use once we implement string support.
+"""
+
+from ritz.syntax import *
+
+
+@component
+def TextInput():
+    """Counter that demonstrates reactive updates (placeholder for text input)."""
+    count = signal(0)  # Integer signal - works!
+
+    def increment():
+        """Increment counter."""
+        count = count + 1
+
+    def decrement():
+        """Decrement counter."""
+        count = count - 1
+
+    with Div(class_="container"):
+        with H1():
+            yield "Reactive Counter"
+
+        with P(class_="instructions"):
+            yield "Click buttons to see reactive updates (text input coming soon!):"
+
+        # Buttons (placeholder for text input)
+        with Div(class_="button-group"):
+            with Button(onclick=decrement):
+                yield "−"
+
+            with P(class_="counter-display"):
+                yield f"Count: {count}"
+
+            with Button(onclick=increment):
+                yield "+"
+
+        # Info about what we need
+        with P(class_="todo"):
+            yield "TODO: Replace with text input once we implement:"
+        with Ul(class_="todo-list"):
+            with Li():
+                yield "1. String signals (i8* not i32)"
+            with Li():
+                yield "2. oninput event handler"
+            with Li():
+                yield "3. Event value passing"
+            with Li():
+                yield "4. F-string interpolation with signals"