Split the simulation from presentation into an SDL-free library

Sim holds one whole game (tick, snapshots, checksum) and talks to the screen only
through Cues, which the client's Scene plays and the server ignores. All drawing
moved to scene.cpp. Match takes this screen's wishes as request flags instead of
reading the menu, input and settings. The sim library builds without SDL and the
server links it, ready to run games itself.

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

src/chat.cpp

@@ -92,7 +92,7 @@ void Chat::players_clear()
 int Chat::member_get(Game& game, int fighter)
 {
     if (game.session.isActive)
-        return game.match.owners[fighter];
+        return game.sim.match.owners[fighter];
     return fighter == game.local ? game.net.selfId : NO_MEMBER;
 }
 
@@ -267,8 +267,8 @@ void Chat::command(Game& game, const std::string& text)
             if (SDL_strcasecmp(argument.c_str(), COLOR_NAMES[color]) != 0)
                 continue;
             int own = game.session.fighter_get(game, game.net.selfId);
-            for (int i = 0; i < game.fighterCount && game.session.isActive; i++)
-                if (i != own && game.match.colors[i] == color)
+            for (int i = 0; i < game.sim.fighterCount && game.session.isActive; i++)
+                if (i != own && game.sim.match.colors[i] == color)
                     return system(std::string(COLOR_NAMES[color]) + " is already taken by another player.");
             game.settings.color = color;
             game.settings.changed();
@@ -284,7 +284,7 @@ void Chat::command(Game& game, const std::string& text)
 Rect Chat::log_area_get(Game& game)
 {
     float bottom = CANVAS_HEIGHT - HOTBAR_MARGIN;
-    MatchState state = (MatchState)game.match.state;
+    MatchState state = (MatchState)game.sim.match.state;
     if (state != MATCH_PRACTICE && state != MATCH_COUNTDOWN)
     {
         RivalLayout rivals = game.ui.rivals_layout(game);
@@ -343,10 +343,10 @@ void Chat::draw(Game& game)
 void Chat::overhead_draw(Game& game)
 {
     float now = seconds_get();
-    float above = game.match.state == MATCH_PRACTICE ? BUBBLE_ABOVE : BUBBLE_MATCH_ABOVE;
-    for (int i = 0; i < game.fighterCount; i++)
+    float above = game.sim.match.state == MATCH_PRACTICE ? BUBBLE_ABOVE : BUBBLE_MATCH_ABOVE;
+    for (int i = 0; i < game.sim.fighterCount; i++)
     {
-        Fighter& fighter = game.fighters[i];
+        Fighter& fighter = game.sim.fighters[i];
         int member = member_get(game, i);
         if (!fighter.isAlive || member == NO_MEMBER)
             continue;