Implement RitzMain() convention and Main.wasm standard

**Convention: RitzMain() entry point**
Every Ritz file now requires a `@component def RitzMain()` as the entry point.
This provides a consistent, predictable entry point for all applications.

**Universal Main.wasm output**
Build system now always outputs Main.wasm instead of ComponentName.wasm.
This means every example uses the exact same HTML boilerplate!

**Changes:**

**Codegen (llvm_codegen_signals.py):**
- Check for RitzMain component at generation time
- Error if RitzMain not found: "No RitzMain component found!"
- Always call `render_RitzMain()` from main() entry point
- Fix: Scope reactive text nodes to components (`@reactive_text_ComponentName_N_node`)
  - Prevents global name collisions when multiple components have reactive text

**Build (build.py):**
- Output Main.wasm in same directory as source file
- Output Main.ll (LLVM IR) for inspection
- Convention over configuration!

**Loader (ritz-runtime.js):**
- Auto-detect component name from WASM filename
- `new RitzLoader().load('Main.wasm')` - no second parameter needed!
- Component name used only for status messages

**Template (examples/template.html):**
- Minimal boilerplate - literally 25 lines
- Just copy and change nothing!
- Loads Main.wasm - works for every example

**Styles (examples/runtime/styles.css):**
- Shared styles for all examples
- Clean, modern defaults
- App container, buttons, inputs, typography

**Example (HighFive):**
```python
@component
def HighFive():
    # ... component logic

@component
def RitzMain():
    """Entry point - required!"""
    yield HighFive()
```

**Result:**
✅ Every example: copy template.html, change nothing
✅ Every example: builds to Main.wasm
✅ Consistent entry point: RitzMain()
✅ No more component name boilerplate

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

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

examples/highfive/HighFive.html

@@ -86,10 +86,10 @@ ritzInstance.exports.increment()</pre>
         // Wait for DOM to be ready
         if (document.readyState === 'loading') {
             document.addEventListener('DOMContentLoaded', () => {
-                new RitzLoader().load('HighFive.wasm', 'HighFive');
+                new RitzLoader().load('Main.wasm');
             });
         } else {
-            new RitzLoader().load('HighFive.wasm', 'HighFive');
+            new RitzLoader().load('Main.wasm');
         }
     </script>
 </body>

examples/highfive/HighFive.py

@@ -24,3 +24,9 @@ def HighFive():
 
         with Button(onclick=increment):
             yield "High Five!"
+
+
+@component
+def RitzMain():
+    """Entry point - required for all Ritz applications."""
+    yield HighFive()

examples/highfive/Main.ll

@@ -0,0 +1,114 @@
+; Generated by Ritz Framework with Signals
+; Components: HighFive, RitzMain
+
+; String constants
+@.str.0 = private unnamed_addr constant [13 x i8] c"High fives: \00"
+@.str.1 = private unnamed_addr constant [4 x i8] c"div\00"
+@.str.2 = private unnamed_addr constant [6 x i8] c"class\00"
+@.str.3 = private unnamed_addr constant [14 x i8] c"high-five-app\00"
+@.str.4 = private unnamed_addr constant [2 x i8] c"p\00"
+@.str.5 = private unnamed_addr constant [25 x i8] c"Give me a high five! ✋\00"
+@.str.6 = private unnamed_addr constant [6 x i8] c"count\00"
+@.str.7 = private unnamed_addr constant [7 x i8] c"button\00"
+@.str.8 = private unnamed_addr constant [6 x i8] c"click\00"
+@.str.9 = private unnamed_addr constant [10 x i8] c"increment\00"
+@.str.10 = private unnamed_addr constant [11 x i8] c"High Five!\00"
+
+; JavaScript bridge function declarations
+declare i32 @js_create_element(i8*)
+declare i32 @js_create_text(i8*)
+declare i32 @js_create_text_with_int(i8*, i32)
+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*)
+declare void @js_update_text_with_int(i32, i8*, i32)
+declare i32 @js_create_marker()
+declare void @js_replace_at_marker(i32, i32, i32)
+
+; Signal storage for HighFive (reactive state in WASM memory)
+@signal_HighFive_high_fives = global i32 0
+
+; Reactive text node storage for HighFive
+@reactive_text_HighFive_0_node = global i32 0
+
+; Signal helper functions
+define i32 @get_high_fives() {
+entry:
+  %val = load i32, i32* @signal_HighFive_high_fives
+  ret i32 %val
+}
+
+define void @set_high_fives(i32 %newval) {
+entry:
+  store i32 %newval, i32* @signal_HighFive_high_fives
+  ; TODO: Trigger DOM update callback
+  ret void
+}
+
+; Event handler: increment
+define void @increment() {
+entry:
+  %var0 = load i32, i32* @signal_HighFive_high_fives
+  %var1 = add i32 %var0, 1
+  store i32 %var1, i32* @signal_HighFive_high_fives
+  %var2 = load i32, i32* @reactive_text_HighFive_0_node
+  %var3 = getelementptr inbounds [13 x i8], [13 x i8]* @.str.0, i32 0, i32 0
+  %var4 = load i32, i32* @signal_HighFive_high_fives
+  call void @js_update_text_with_int(i32 %var2, i8* %var3, i32 %var4)
+  ret void
+}
+
+; Component render function
+define i32 @render_HighFive() {
+entry:
+  %var6 = getelementptr inbounds [4 x i8], [4 x i8]* @.str.1, i32 0, i32 0
+  %var5 = call i32 @js_create_element(i8* %var6)
+  %var7 = getelementptr inbounds [6 x i8], [6 x i8]* @.str.2, i32 0, i32 0
+  %var8 = getelementptr inbounds [14 x i8], [14 x i8]* @.str.3, i32 0, i32 0
+  call void @js_set_attribute(i32 %var5, i8* %var7, i8* %var8)
+  %var10 = getelementptr inbounds [2 x i8], [2 x i8]* @.str.4, i32 0, i32 0
+  %var9 = call i32 @js_create_element(i8* %var10)
+  %var11 = call i32 @js_create_text(i8* getelementptr inbounds ([25 x i8], [25 x i8]* @.str.5, i32 0, i32 0))
+  call void @js_append_child(i32 %var9, i32 %var11)
+  call void @js_append_child(i32 %var5, i32 %var9)
+  %var13 = getelementptr inbounds [2 x i8], [2 x i8]* @.str.4, i32 0, i32 0
+  %var12 = call i32 @js_create_element(i8* %var13)
+  %var14 = getelementptr inbounds [6 x i8], [6 x i8]* @.str.2, i32 0, i32 0
+  %var15 = getelementptr inbounds [6 x i8], [6 x i8]* @.str.6, i32 0, i32 0
+  call void @js_set_attribute(i32 %var12, i8* %var14, i8* %var15)
+  %var16 = getelementptr inbounds [13 x i8], [13 x i8]* @.str.0, i32 0, i32 0
+  %var17 = load i32, i32* @signal_HighFive_high_fives
+  %var18 = call i32 @js_create_text_with_int(i8* %var16, i32 %var17)
+  store i32 %var18, i32* @reactive_text_HighFive_0_node
+  call void @js_append_child(i32 %var12, i32 %var18)
+  call void @js_append_child(i32 %var5, i32 %var12)
+  %var20 = getelementptr inbounds [7 x i8], [7 x i8]* @.str.7, i32 0, i32 0
+  %var19 = call i32 @js_create_element(i8* %var20)
+  %var21 = getelementptr inbounds [6 x i8], [6 x i8]* @.str.8, i32 0, i32 0
+  %var22 = getelementptr inbounds [10 x i8], [10 x i8]* @.str.9, i32 0, i32 0
+  call void @js_bind_event(i32 %var19, i8* %var21, i8* %var22)
+  %var23 = call i32 @js_create_text(i8* getelementptr inbounds ([11 x i8], [11 x i8]* @.str.10, i32 0, i32 0))
+  call void @js_append_child(i32 %var19, i32 %var23)
+  call void @js_append_child(i32 %var5, i32 %var19)
+  ret i32 %var5
+}
+
+; Reactive text node storage for RitzMain
+@reactive_text_RitzMain_0_node = global i32 0
+
+; Component render function
+define i32 @render_RitzMain() {
+entry:
+  %var24 = call i32 @render_HighFive()
+  ret i32 %var24
+}
+
+; Main entry point
+define void @main() {
+entry:
+  %root = call i32 @render_RitzMain()
+  call void @js_set_root(i32 %root)
+  ret void
+}