initial proper subfooter unit tests

tests/suite/layout/grid/subfooters.typ

@@ -22,6 +22,7 @@
     [*Mode*], [2025],
     table.cell(colspan: 2)[*Totals*],
   ),
+  // TODO: Why does it overflow here?
   table.header(
     level: 2,
     table.cell(colspan: 2)[*United States*],
@@ -39,3 +40,143 @@
     table.cell(colspan: 2)[*Data Inc.*],
   ),
 )
+
+--- grid-subfooters-basic ---
+#grid(
+  [a],
+  grid.footer(level: 2, [b]),
+  grid.footer([c]),
+)
+
+--- grid-subfooters-basic-non-consecutive ---
+#grid(
+  [x],
+  grid.footer(level: 2, [a]),
+  [y],
+  grid.footer([b]),
+)
+
+--- grid-subfooters-basic-replace ---
+#grid(
+  [x],
+  grid.footer(level: 2, [a]),
+  [y],
+  grid.footer(level: 2, [b]),
+  [z],
+  grid.footer([c]),
+)
+
+--- grid-subfooters-basic-with-header ---
+#grid(
+  grid.header([a]),
+  [b],
+  grid.footer(level: 2, [c]),
+  grid.footer([d]),
+)
+
+--- grid-subfooters-basic-non-consecutive-with-header ---
+#grid(
+  grid.header([a]),
+  [x],
+  grid.footer(level: 2, [b]),
+  [y],
+  grid.footer([f])
+)
+
+--- grid-subfooters-repeat ---
+#set page(height: 8em)
+#grid(
+  ..([a],) * 10,
+  grid.footer(level: 2, [b]),
+  grid.footer([c]),
+)
+
+--- grid-subfooters-repeat-non-consecutive ---
+#set page(height: 8em)
+#grid(
+  ..([y],) * 10,
+  grid.footer(level: 2, [b]),
+  [x],
+  grid.footer([a]),
+)
+
+--- grid-subfooters-repeat-with-header ---
+#set page(height: 8em)
+#grid(
+  grid.header([a]),
+  ..([b],) * 10,
+  grid.footer(level: 2, [c]),
+  [m],
+  grid.footer([f])
+)
+
+--- grid-subfooters-repeat-gutter ---
+// Gutter above the footer is also repeated
+#set page(height: 8em)
+#grid(
+  inset: (top: 0.5pt),
+  stroke: (top: 1pt),
+  gutter: (1pt,) * 9 + (6pt, 1pt),
+  ..([a],) * 10,
+  grid.footer(level: 2, [b]),
+  grid.footer([c]),
+)
+
+--- grid-subfooters-repeat-replace ---
+#set page(height: 8em)
+#grid(
+  ..([x],) * 10,
+  grid.footer(level: 2, [a]),
+  ..([y],) * 10,
+  grid.footer(level: 2, [b]),
+  [z],
+  grid.footer([c]),
+)
+
+--- grid-subfooters-repeat-replace-multiple-levels ---
+// TODO: This is overflowing
+#set page(height: 8em)
+#grid(
+  ..([x],) * 6,
+  grid.footer(level: 2, [a]),
+  ..([y],) * 10,
+  grid.footer(level: 3, [b]),
+  grid.footer(level: 2, [c]),
+  [z],
+  grid.footer([d]),
+)
+
+--- grid-subfooters-repeat-replace-gutter ---
+#set page(height: 8em)
+#grid(
+  gutter: 3pt,
+  ..([x],) * 3,
+  grid.footer(level: 2, [a]),
+  ..([y],) * 8,
+  grid.footer(level: 2, [b]),
+  [z],
+  grid.footer([c]),
+)
+
+--- grid-subfooters-repeat-replace-widow ---
+#set page(height: 8em)
+#grid(
+  ..([x],) * 14,
+  grid.footer(level: 2, [a]),
+  ..([y],) * 8,
+  grid.footer(level: 2, [b]),
+  [z],
+  grid.footer([c]),
+)
+
+--- grid-subfooters-repeat-replace-double-widow ---
+#set page(height: 8em)
+#grid(
+  ..([x],) * 12,
+  grid.footer(level: 3, [a]),
+  grid.footer(level: 2, [b]),
+  ..([y],) * 11,
+  grid.footer(level: 2, [c]),
+  [z],
+  grid.footer([d]),
+)