Co-op offline with an AI partner

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

src/menu.rs

@@ -279,6 +279,7 @@ enum Btn {
     MatchCoopNext,
     MatchCoopCreate,
     MatchCoopSource, // switch between the built-in campaign and the editor campaign
+    MatchCoopSolo,   // the selected co-op mission without the server, with an AI partner
     MatchTake(usize),
     MatchAi(usize),
     MatchTeam(usize), // next team for that seat
@@ -397,6 +398,7 @@ pub enum MenuAction {
     MatchCreate,
     MatchCoopCreate(usize),
     MatchCoopEditorCreate(usize), // co-op match of a mission of `campaign_doc`
+    MatchCoopSolo(Option<crate::campaign_doc::CampaignDoc>, usize), // offline with an AI partner: editor campaign or built-in, mission
     MatchTakeSide(u8),
     MatchSetAi(u8, bool),
     MatchSetTeam(u8, u8, bool), // side, team, the own seat
@@ -798,6 +800,8 @@ impl Menu {
                 self.confirm = None;
                 MenuAction::Consumed
             }
+            Some(Btn::MatchCoopSolo) if self.coop_editor => MenuAction::MatchCoopSolo(Some(self.coop_doc().clone()), self.coop_editor_mission),
+            Some(Btn::MatchCoopSolo) => MenuAction::MatchCoopSolo(None, self.coop_mission),
             Some(Btn::MatchCoopCreate) if self.coop_editor => MenuAction::MatchCoopEditorCreate(self.coop_editor_mission),
             Some(Btn::MatchCoopCreate) => MenuAction::MatchCoopCreate(self.coop_mission),
             Some(Btn::MatchReady) => MenuAction::MatchReady(!self.match_ui.ready),
@@ -1992,6 +1996,7 @@ impl Menu {
                     items.push((Btn::MatchCoopPrev, "<".to_string()));
                     items.push((Btn::MatchCoopCreate, tr("net.coop_create")));
                     items.push((Btn::MatchCoopNext, ">".to_string()));
+                    items.push((Btn::MatchCoopSolo, tr("net.coop_solo")));
                 }
                 // the button names what comes next
                 let next = match (editor_coop, self.coop_league) {