Fix nested components - render functions now return i32

Changes:
- Component render functions return i32 (root element) instead of void
- Nested components (yield SomeComponent()) now work correctly
- Added main() entry point that calls top-level component and sets root
- Updated runtime to call main() instead of render_ComponentName()

Note: Active state in ternary expressions still needs reactive updates
This commit fixes the nested component rendering issue

All tests passing (51 passed, 2 skipped)

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

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

examples/runtime/ritz-runtime.js

@@ -306,15 +306,13 @@ class RitzLoader {
 
             this.setStatus(`⏳ Rendering ${componentName}...`);
 
-            // Call the render function with props
-            const renderFn = instance.exports[`render_${componentName}`];
-            if (!renderFn) {
-                throw new Error(`render_${componentName} not found in WASM exports`);
+            // Call the main entry point (which renders top-level component and sets root)
+            const mainFn = instance.exports.main;
+            if (!mainFn) {
+                throw new Error(`main function not found in WASM exports`);
             }
 
-            // Pass props as positional arguments
-            const propValues = Object.values(props);
-            renderFn(...propValues);
+            mainFn();
 
             // Update signals
             runtime.updateSignals();