fix: doc rendering — markdown prose styling, code blocks with copy button, proper step parsing

- Add @tailwindcss/typography plugin for prose styling
- Create CodeBlock component with copy button and language labels
- Create Md wrapper component using ReactMarkdown with custom renderers
- Replace all plain text renders with Md for proper markdown formatting
- Fix parseSteps() in pipeline to group numbered steps with code blocks
- Add First Task subtitle explaining its purpose
- Add conditional file.purpose render in module key files

apps/web/src/app/globals.css

@@ -1,4 +1,5 @@
 @import "tailwindcss";
+@plugin "@tailwindcss/typography";
 
 :root {
   --background: #0a0a0f;