Fix city generation retries and remove city-wide economy mechanics

proto/city.proto

@@ -7,19 +7,11 @@ message Subscribe { Rect rect = 1; uint32 lod = 2; }
 message Ping { uint32 nonce = 1; }
 message Propose { uint32 speed = 1; }
 message Vote { bool yes = 1; }
-// Equal rights for every connected player; only these three bounded actions exist.
-message Intervene { string action = 1; }
-message Needs { uint32 hunger = 1; uint32 fatigue = 2; uint32 morale = 3; }
-message GameEvent { uint64 minute = 1; string kind = 2; }
-message Gameplay {
-  sint64 treasury = 1; uint64 food = 2; Needs needs = 3;
-  repeated GameEvent events = 4; repeated string pending = 5;
-  uint64 minute = 6; uint64 next_intervention_minute = 7;
-}
 message CreateCity { repeated double bbox = 1; string name = 2; uint32 seed = 3; }
 message CityJob { string id = 1; string city_id = 2; string status = 3; string room_id = 4; string error = 5; string stage = 6; }
 message ClientMessage {
-  oneof body { Join join = 1; Subscribe subscribe = 2; Ping ping = 3; Propose propose = 4; Vote vote = 5; Intervene intervene = 6; }
+  reserved 6;
+  oneof body { Join join = 1; Subscribe subscribe = 2; Ping ping = 3; Propose propose = 4; Vote vote = 5; }
 }
 message Agent { uint32 id = 1; sint32 x = 2; sint32 y = 3; uint32 kind = 4; }
 message Welcome { string room = 1; uint64 tick = 2; string city_manifest_url = 3; string session = 4; uint32 protocol_version = 5; }
@@ -29,7 +21,8 @@ message Error { string code = 1; string message = 2; }
 message VoteState { bool active = 1; uint32 speed = 2; uint32 yes = 3; uint32 players = 4; uint32 remaining_seconds = 5; }
 message Clock { uint64 tick = 1; double game_seconds = 2; uint32 speed = 3; }
 message ServerMessage {
-  oneof body { Welcome welcome = 1; Snapshot snapshot = 2; Delta delta = 3; Error error = 4; Ping pong = 5; VoteState vote_state = 6; Clock clock = 7; Gameplay gameplay = 8; }
+  reserved 8;
+  oneof body { Welcome welcome = 1; Snapshot snapshot = 2; Delta delta = 3; Error error = 4; Ping pong = 5; VoteState vote_state = 6; Clock clock = 7; }
 }
 message SavedAgent { uint32 id = 1; uint32 route = 2; double distance = 3; }
 message Route { repeated sint32 xy = 1; string home_id = 2; string workplace_id = 3; }
@@ -38,5 +31,5 @@ message RoomSave {
   uint64 tick = 5; uint64 seed = 6; double game_seconds = 7; uint32 speed = 8;
   repeated SavedAgent agents = 9; repeated Route routes = 10;
   string city_revision = 11;
-  Gameplay gameplay = 12;
+  reserved 12; // Retired city-wide economy in snapshot v2.
 }