site: fix mobile horizontal overflow in process/roadmap section

The "diagnostic sprint" week-cards used a fixed repeat(3, 1fr) grid that
didn't collapse on narrow viewports, pushing page width to 553px on a
390px phone (horizontal scroll). Switched to the responsive
repeat(auto-fit, minmax(220px, 1fr)) pattern already used elsewhere in
this file. Verified: mobile docWidth now equals viewport (390=390).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017zfynhEadteeMKwYFAq4V8

Author: jlynshue

src/pages/Redesign.tsx

@@ -308,7 +308,7 @@ const Redesign = () => {
         <div
           style={{
             display: "grid",
-            gridTemplateColumns: "repeat(3, 1fr)",
+            gridTemplateColumns: "repeat(auto-fit, minmax(220px, 1fr))",
             gap: "var(--s-5)",
           }}
         >