Implement Python → LLVM IR → WASM reactive framework

MAJOR ACHIEVEMENT: Full working reactive framework!

## What's Working

✅ Python → AST → Ritz IR → LLVM IR → WASM pipeline
✅ Reactive signals stored in WASM memory (@signal_name = global i32)
✅ Event handlers exported from WASM and callable from JS
✅ Clean runtime with RitzLoader and debug tools
✅ Two working examples: HelloWorld and HighFive counter

## Core Components

### Parser (ritz/parser.py)
- Uses Python's ast module to parse components
- Handles @component decorator, signals, event handlers
- Supports yield, with statements, f-strings, augmented assignment (+=)
- Clean syntax: from ritz.syntax import *

### LLVM IR Code Generator (ritz/llvm_codegen_signals.py)
- Generates LLVM IR directly (not C!)
- Signals as global variables in WASM memory
- Exports getter/setter functions for each signal
- Exports event handler functions for JS to call
- UTF-8 string handling

### Build System (ritz/build.py)
- Python → AST → IR → LLVM IR → clang --target=wasm32 → WASM
- Saves intermediate .ll files for inspection
- Debug symbols support (-g flag)

### Runtime (runtime/ritz-runtime.js)
- RitzRuntime class: DOM bridge for WASM
- RitzLoader class: Simplified component loading
- Debug bar with Ctrl+` toggle
- Signal updates trigger DOM updates

## Examples

### HelloWorld.py
Simple static content - renders <p>Hello World</p>

### HighFive.py
Reactive counter with:
- Signal in WASM memory (high_fives = signal(0))
- Event handler (increment function)
- DOM updates on signal change

## Test Coverage

- 4 parser tests (all passing)
- 4 LLVM codegen tests (all passing)
- 4 signal parsing tests (all passing)
- Code formatted with black and ruff

## Next Steps

- <script type="text/ritz"> in-browser compilation
- Better signal-to-DOM binding tracking
- More complex examples (TodoMVC, forms, lists)
- Playwright browser tests

---

This is a genuinely innovative framework: write Python, compile to WASM,
run with reactive signals in WASM memory. No virtual DOM, no transpilation,
just compiled Python with fine-grained reactivity.

🎉 Python → WASM → Reactive UI is REAL!

examples/HelloWorld.ll

@@ -0,0 +1,25 @@
+; Generated by Ritz Framework with Signals
+; Component: HelloWorld
+
+; String constants
+@.str.0 = private unnamed_addr constant [2 x i8] c"p\00"
+@.str.1 = private unnamed_addr constant [12 x i8] c"Hello World\00"
+
+; JavaScript bridge function declarations
+declare i32 @js_create_element(i8*)
+declare i32 @js_create_text(i8*)
+declare void @js_append_child(i32, i32)
+declare void @js_set_attribute(i32, i8*, i8*)
+declare void @js_set_root(i32)
+declare void @js_bind_event(i32, i8*, i8*)
+declare void @js_update_text_content(i32, i8*)
+
+; Component render function
+define void @render_HelloWorld() {
+entry:
+  %var0 = call i32 @js_create_element(i8* getelementptr inbounds ([2 x i8], [2 x i8]* @.str.0, i32 0, i32 0))
+  %var1 = call i32 @js_create_text(i8* getelementptr inbounds ([12 x i8], [12 x i8]* @.str.1, i32 0, i32 0))
+  call void @js_append_child(i32 %var0, i32 %var1)
+  call void @js_set_root(i32 %var0)
+  ret void
+}