feat(blox): add steps block

Steps block:
- Three layouts: vertical (stacked with connector line), horizontal
  (side-by-side, connector above), timeline (alternating cards on centre
  line)
- Three marker styles: number (decimal/padded/roman/alpha), icon, dot
- Layout-aware marker sizing - bare 40px icon for horizontal, tinted
  circle for vertical/timeline
- Staggered IntersectionObserver entrance animation
- Code span rendering in step body text
- Added to startup-landing-page template as a horizontal how-it-works
  section

scripts/check-template-deps.mjs

@@ -1,5 +1,5 @@
 #!/usr/bin/env node
-import { readFileSync, readdirSync, statSync } from "node:fs";
+import { readdirSync, readFileSync, statSync } from "node:fs";
 import { join, resolve } from "node:path";
 
 const REQUIRED = ["tailwindcss", "@tailwindcss/cli"];