refactor(config): remove unused sidebar items and adjust structure

- Remove 'Welcome' section from sidebar configuration
- Retain 'Getting Started' section with autogenerate enabled

Author: fulleni

astro.config.mjs

@@ -15,13 +15,6 @@ export default defineConfig({
 				},
 			],
 			sidebar: [
-				{
-					label: 'Welcome',
-					items: [
-						{ label: 'Introduction', slug: 'welcome/introduction' },
-						// { label: 'Core Philosophy', slug: 'welcome/core-philosophy' },
-					],
-				},
 				{
 					label: 'Getting Started',
 					autogenerate: { directory: 'getting-started' },