fix(website): align the briefing grid to the top, not the centre

Centring made the form's position depend on the cover's height: the cover
is 477px against a 390px ask column, so the primary action was pushed down
43px, and would move again if the document gained a chapter. Measured
393px -> 350px from the section top (it was 618px before this redesign).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: blove

apps/website/src/styles/landing.css

@@ -2061,7 +2061,10 @@ a.preflight-row:hover .preflight-challenge {
   display: grid;
   grid-template-columns: minmax(0, 1fr) 400px;
   gap: 64px;
-  align-items: center;
+  /* Top, not centre. The cover is taller than the ask, so centring pushed the
+   * form down by half the difference (measured: 43px) and made the position of
+   * the section's primary action depend on how many chapters the document has. */
+  align-items: start;
 }
 .teams-eyebrow {
   margin-bottom: 18px;