Final missions above ground (M30, co-op M20), surface option for versus matches, docs

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

src/lobby.rs

@@ -90,6 +90,7 @@ pub struct StartInfo {
     pub teams: Vec<(u8, u8)>, // (side, team) of a versus match
     pub next: bool, // the next mission of a running editor campaign co-op match
     pub carry: Vec<(u8, crate::campaign::Carry)>, // what every side brings into that mission
+    pub surface: bool, // a free match whose eastern half lies above ground
 }
 
 #[derive(Clone, Debug, Default)]
@@ -223,6 +224,18 @@ impl MatchClient {
         self.send_create(sides, map_w, map_h, difficulty, None);
     }
 
+    // a free match; `surface`: its eastern half lies above ground
+    pub fn create_land(&mut self, sides: &[u8], map_w: usize, map_h: usize, difficulty: u8, surface: bool) {
+        let n = self.outbox.len();
+        self.send_create(sides, map_w, map_h, difficulty, None);
+        if let (true, Some(text)) = (surface, self.outbox.get_mut(n)) {
+            if let Ok(mut msg) = serde_json::from_str::<Value>(text) {
+                msg["surface"] = json!(true);
+                *text = msg.to_string();
+            }
+        }
+    }
+
     pub fn create_coop(&mut self, mission: usize, sides: &[u8], map_w: usize, map_h: usize, difficulty: u8) {
         self.send_create(sides, map_w, map_h, difficulty, Some(mission));
     }
@@ -550,7 +563,8 @@ impl MatchClient {
         // a resumed editor campaign run goes on like the next mission of a running one
         let resume = editor && v.get("resume").and_then(|x| x.as_bool()).unwrap_or(false);
         let carry: Vec<(u8, crate::campaign::Carry)> = if resume { v.get("carry").cloned().and_then(|c| serde_json::from_value(c).ok()).unwrap_or_default() } else { Vec::new() };
-        self.start = Some(StartInfo { seed, map_w, map_h, difficulty, sides, local_side, mission, ai, doc, editor, teams, next: resume, carry });
+        let surface = v.get("surface").and_then(|x| x.as_bool()).unwrap_or(false);
+        self.start = Some(StartInfo { seed, map_w, map_h, difficulty, sides, local_side, mission, ai, doc, editor, teams, next: resume, carry, surface });
         self.error = None;
         self.status = None;
     }
@@ -581,7 +595,7 @@ impl MatchClient {
             }
             r.ai = ai.clone();
         }
-        self.start = Some(StartInfo { seed, map_w, map_h, difficulty, sides, local_side, mission: Some(mission), ai, doc: Some(doc), editor: true, teams, next: true, carry });
+        self.start = Some(StartInfo { seed, map_w, map_h, difficulty, sides, local_side, mission: Some(mission), ai, doc: Some(doc), editor: true, teams, next: true, carry, surface: false });
         self.error = None;
     }