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/tabs/TabsClean.py

@@ -0,0 +1,70 @@
+"""
+Cleaner Tabs implementation using wrapper components to reduce repetition.
+"""
+
+from ritz.syntax import *
+
+
+@component
+def VerticalTab(label, is_active, tab_value):
+    """Reusable vertical tab button with active state handling."""
+    # Note: In current implementation, we still need the if/else for class
+    # But it's encapsulated in one place instead of repeated everywhere
+    if is_active:
+        with Button(class_="vertical-tab active"):
+            yield label
+    else:
+        with Button(class_="vertical-tab"):
+            yield label
+
+
+@component
+def VerticalTabs():
+    """Vertical tabs for settings categories."""
+    setting_tab = signal(0)
+
+    def set_setting(value):
+        setting_tab = value
+
+    with Div(class_="vertical-tabs"):
+        # Vertical tab menu
+        with Div(class_="vertical-tab-menu"):
+            # Now each tab is just one line instead of 6!
+            yield VerticalTab("⚙️ General", setting_tab == 0, 0)
+            yield VerticalTab("🔒 Privacy", setting_tab == 1, 1)
+            yield VerticalTab("🚀 Advanced", setting_tab == 2, 2)
+
+        # Tab content (same as before)
+        with Div(class_="vertical-tab-content"):
+            match setting_tab:
+                case 0:
+                    with Div(class_="setting-pane"):
+                        with H3():
+                            yield "⚙️ General Settings"
+                        with P():
+                            yield "Language: English"
+                        with P():
+                            yield "Time Zone: UTC"
+
+                case 1:
+                    with Div(class_="setting-pane"):
+                        with H3():
+                            yield "🔒 Privacy Settings"
+                        with P():
+                            yield "Data Collection: Disabled"
+                        with P():
+                            yield "Analytics: Opt-out"
+
+                case 2:
+                    with Div(class_="setting-pane"):
+                        with H3():
+                            yield "🚀 Advanced Settings"
+                        with P():
+                            yield "Debug Mode: Off"
+                        with P():
+                            yield "Experimental Features: Disabled"
+
+                case _:
+                    with Div(class_="setting-pane"):
+                        with P():
+                            yield "Invalid setting"