Versus map size on the match page; the size sets the number of seats

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

src/lobby.rs

@@ -673,6 +673,17 @@ fn teams_from(sides: &[u8], v: Option<&Value>) -> Vec<(u8, u8)> {
     sides.iter().copied().zip(teams).collect()
 }
 
+// versus map sizes and how many master seats each one has
+pub const MATCH_SIZES: [usize; 7] = [80, 96, 128, 160, 192, 224, 256];
+
+pub fn seats_for(size: usize) -> &'static [u8] {
+    match size {
+        0..=80 => &[0, 2],
+        81..=96 => &[0, 2, 3],
+        _ => &[0, 2, 3, 4],
+    }
+}
+
 fn seats_from(v: Option<&Value>) -> Vec<SeatInfo> {
     v.and_then(|x| x.as_array())
         .map(|arr| {