Plugins: server plugins know the map and hear it change

On a dedicated server reskate.level.current() was empty and level_loaded and level_unloading never
fired, so a server plugin could not tell which map ran or that it had changed. The server's
plugins are now told the map's level each tick, named as players' games name it (a destination's
level, after its "|"). When the server changes the map, they hear level_unloading for the old one
and level_loaded for the new one, as a game's plugins do; players load it after.

dingosdk_server_plugin_tests checks level.current() and both events across a map change.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Hs7xxJDf6SDcQUaXnzmtL5

Server/server_plugins.cpp

@@ -210,6 +210,9 @@ void ServerPlugins::tick(std::uint64_t now_us) {
         }
         const double dt = s.last_tick ? static_cast<double>(now_us - s.last_tick) / 1000.0 : 0;
         s.last_tick = now_us;
+        // The map the server runs, so plugins hear level_unloading and level_loaded when it
+        // changes, as a game's plugins do (when the server changes it; players load it after).
+        s.plugins.set_level(s.server.map_level());
         s.plugins.tick(dt);
         for (auto &bytes : std::exchange(s.environment.outbox, {})) s.server.send_plugin_message(wire::to_of(bytes), bytes);
     } catch (const std::exception &error) {