Widen narrative rail from 248px to 320px

At 248px the body text in every section's rail was wrapping after
~36 chars per line, which broke phrases mid-clause and made the
takeaway feel cramped. 320px lands around 50-55 chars per line —
inside the comfortable 45-75 reading range — without eating
meaningfully into the demo column on a 1440px+ viewport. Bumped the
column gap from 32 → 40px to keep the rail visually distinct from
the demo card now that they sit at similar weights.

Co-authored-by: Cursor <cursoragent@cursor.com>

assets/styles/layout.css

@@ -91,12 +91,15 @@ section:last-of-type { border-bottom: none; }
    into a live margin note rather than a post-mortem.
 
    Layout math: container.wide is 1080px max with 32px padding =>
-   1016px usable. 248px rail + 32px gap + 736px demo. Below 900px we
+   320px rail + 40px gap + demo claims the rest. The rail width was
+   bumped from 248 → 320px so the narrative breathes (~50-55 chars per
+   line of body text vs ~36 before) — at 248 every lede was wrapping
+   on awkward stop-words and the takeaway felt cramped. Below 900px we
    collapse to single-column and unstick the rail. */
 .section--two-col {
   display: grid;
-  grid-template-columns: 248px 1fr;
-  column-gap: 32px;
+  grid-template-columns: 320px 1fr;
+  column-gap: 40px;
   align-items: start;
   /* Land cleanly under the sticky header on anchor jumps (#folding). */
   scroll-margin-top: 104px;
@@ -115,7 +118,7 @@ section:last-of-type { border-bottom: none; }
   scrollbar-width: thin;
 }
 /* The 640px cap on .lede / .takeaway exists to keep line length
-   readable in the single-column layout. Inside a 248px rail that cap
+   readable in the single-column layout. Inside a 320px rail that cap
    is moot — drop it so the text fills the rail. */
 .section--two-col .section-narrative .lede,
 .section--two-col .section-narrative .takeaway {