homepage: sections are horizontal rows, not columns

Each section's panels fill an auto-fill row (as many per row as the
viewport allows) and the sections stack vertically — the side-by-side
column layout was the wrong read of 'render the sections horizontally'.

tests/homepage_pages.bats

@@ -34,10 +34,11 @@ setup() {
     grep -q "SECTION_ORDER" "$BASE/app.js"
 }
 
-@test "sections render horizontally (one column per section)" {
+@test "sections render as horizontal rows of panels" {
     grep -q 'class="sections"' "$BASE/index.html"
     grep -q 'class="sections"' "$BASE/admin.html"
-    grep -q "repeat(auto-fit" "$BASE/style.css"
+    # Each section's panels fill an auto-fill row, not a single column.
+    grep -q "repeat(auto-fill" "$BASE/style.css"
 }
 
 @test "WIP badges distinguish open from closed work" {