Keep posts with code inside a phone's width

The single-column layout grew to its widest line, so a code block pushed the
whole text past the edge of the screen.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

landing/src/app/ui/_detail.scss

@@ -32,6 +32,10 @@
 // ending in a dead end.
 .content-page__layout {
   display: grid;
+  // One column below the desktop layout, and one that may shrink: an
+  // implicit `auto` track grows to its widest line, and a code block in a
+  // post pushed the whole text past the edge of a phone.
+  grid-template-columns: minmax(0, 1fr);
   gap: 3rem;
   padding-bottom: 5rem;