Fix costume merging, restrict server names, add Centrix tag

- Mod merge: rebuild a merged bundle's chunk metadata the way the game
  writes it (one record per chunk, in chunk GUID order), so costumes
  from different mods built on the same game costume keep their
  textures and meshes
- Merge audit checks that layout, and there is a new unit test for it
- Server names: only letters, numbers, spaces and - _ [ ] ( ),
  1 to 64 characters; the server browser hides servers with other names
- New Centrix tag from the backend's "centrix" list: blue and white
  name, badge and item animation, ranked after Dev and before Creator

Extension/Multiplayer/Test/developer_identity_tests.cpp

@@ -33,12 +33,12 @@ void parsing() {
         R"({"categories":{"dev":["76561198000000002","76561198000000001","76561198000000002"],)"
         R"("homie":["76561198000000003"],"content_creator":["76561198000000004"]}})");
     check(lists[0] == std::vector{dev, other_dev} && lists[1] == std::vector{homie} && lists[2] == std::vector{creator} &&
-              lists[3].empty(),
+              lists[3].empty() && lists[4].empty(),
           "The backend's answer was not read as its three lists, with nobody banned");
     // The ban list comes beside the categories; a player can be in both.
     const auto bans = parse_identity_lists(
         R"({"categories":{"dev":["76561198000000001"]},"banned":["76561198000000005","76561198000000001","76561198000000005"]})");
-    check(bans[0] == std::vector{dev} && bans[3] == std::vector{dev, stranger}, "The ban list was not read");
+    check(bans[0] == std::vector{dev} && bans[static_cast<std::size_t>(L::banned)] == std::vector{dev, stranger}, "The ban list was not read");
     // A newer backend may list more categories and fields, and an older one fewer.
     const auto partial = parse_identity_lists(
         R"({"updated":"2026-10-04","categories":{"moderator":["76561198000000005"],"dev":["76561198000000001"]}})");
@@ -72,7 +72,7 @@ void lookup() {
           "A player was found in a list they are not in");
     check(!reskate_developer(0) && !identity_listed(dev, L::count), "No player, or no list, matched");
     check(!reskate_banned(dev) && !reskate_banned(stranger), "Someone is banned though the lists ban nobody");
-    check(publish_identity_lists({{{dev, other_dev}, {homie}, {creator}, {dev, stranger}}}) && reskate_banned(stranger) &&
+    check(publish_identity_lists({{{dev, other_dev}, {homie}, {creator}, {}, {dev, stranger}}}) && reskate_banned(stranger) &&
               reskate_banned(dev) && reskate_developer(dev) && !reskate_banned(other_dev) && !reskate_banned(0),
           "The ban list did not ban exactly the players on it");
     check(publish_identity_lists({{{dev, other_dev}, {homie}, {creator}}}) && !reskate_banned(stranger), "A lifted ban stayed");
@@ -82,6 +82,16 @@ void lookup() {
               identity_mark(creator) == L::content_creator && identity_mark(homie) == L::homie && !identity_mark(stranger) &&
               !identity_mark(0),
           "A player's mark is not the first list they are on");
+    // Centrix: read from the answer as its own list, and its mark comes after a developer's and
+    // before a content creator's.
+    const auto centrix = parse_identity_lists(R"({"categories":{"centrix":["76561198000000005"],"dev":["76561198000000001"]}})");
+    check(centrix[static_cast<std::size_t>(L::centrix)] == std::vector{stranger} && centrix[static_cast<std::size_t>(L::banned)].empty(),
+          "The Centrix list was not read as its own");
+    check(publish_identity_lists({{{dev}, {homie, stranger}, {creator, stranger}, {dev, creator, stranger}}}) &&
+              identity_mark(dev) == L::developer && identity_mark(stranger) == L::centrix && identity_mark(creator) == L::centrix &&
+              identity_mark(homie) == L::homie && !reskate_banned(stranger),
+          "Centrix is not marked after a developer and before a content creator");
+    check(publish_identity_lists({{{dev}, {dev, homie, creator}, {dev, creator}}}), "The lists did not go back");
     // Their tag and their items are each their own to hide.
     check(own_tag_shown() && own_items_shown(), "A player's tag or items start hidden");
     show_own_tag(false);