chore(docs-site): add dev shortcut and fix hero heading clipping

- Add `pnpm docs` script that frees port 3000 then runs the docs-site
  dev server, so the docs preview is one command away.
- Bump hero heading line-height to 1.2 and add 0.15em bottom padding
  so the gradient text-clip no longer cuts off descenders.
- Sync auto-generated next-env.d.ts to the current Next types path.

docs-site/content/docs/getting-started/introduction.mdx

@@ -16,8 +16,9 @@ import { ProductMechanics } from "@/components/product-mechanics";
         backgroundClip: 'text',
         color: 'transparent',
         WebkitTextFillColor: 'transparent',
-        lineHeight: '1.1',
+        lineHeight: '1.2',
         letterSpacing: '0',
+        paddingBottom: '0.15em',
       }}
     >
       Make analytics context usable by agents