[Server] Instrument command processing, game starts, and event loops

Add a lock-free MetricsRegistry that accumulates per-command processing
times in preallocated histogram slots (one per protobuf command type,
bucketed at 1/5/10/25/50/100/250/500/1000/2500/5000 ms +Inf). The
hot-path observeCommand() uses only relaxed atomic adds — no locks,
no allocations, no cache-line ping-pong beyond the unavoidable counter
updates.

Wire the registry into AbstractServerSocketInterface::processCommandContainer()
so every processed command is attributed with its container's wall-clock
time. When a container exceeds metrics/slow_command_ms (default 500),
a warning is logged including the connected username.

Add an EventLoopWatchdog heartbeat that runs on every socket pool thread.
If a heartbeat overshoots metrics/stall_warn_ms (default 2000 ms), the
overshoot is recorded in atomic counters and a warning is logged. Both
thresholds are configurable in servatrice.ini; setting stall_warn_ms to 0
disables the watchdogs entirely.

Track game-start durations via a separate histogram in MetricsRegistry.
Server_Game::startGameNow() measures the time from zone creation through
player materialization and reports it via Server::observeGameStartDurationMs().

Add a live card-count gauge: Server_Game exposes getCardsInGame() and
Servatrice::getCardsInGamesTotal() sums across all running games under
the appropriate read locks.

Include a standalone metrics_registry_test (Google Test) that validates
empty registries, single/multi-sample histograms, kind encoding,
overflow-slot collapse, negative-duration clamping, gauge rendering,
and the game-start histogram separation.

Took 10 minutes

libcockatrice_network/libcockatrice/network/server/remote/game/server_abstract_player.cpp

@@ -66,6 +66,15 @@ Server_AbstractPlayer::Server_AbstractPlayer(Server_Game *_game,
 
 Server_AbstractPlayer::~Server_AbstractPlayer() = default;
 
+int Server_AbstractPlayer::getCardCount() const
+{
+    int result = 0;
+    for (auto *zone : zones) {
+        result += zone->getCards().size();
+    }
+    return result;
+}
+
 void Server_AbstractPlayer::prepareDestroy()
 {
     delete deck;

libcockatrice_network/libcockatrice/network/server/remote/game/server_abstract_player.h

@@ -43,6 +43,8 @@ public:
                           Server_AbstractUserInterface *_handler);
     ~Server_AbstractPlayer() override;
     void prepareDestroy() override;
+    /// Total cards across all of this player's zones. The caller must hold the game's mutex.
+    int getCardCount() const;
     const DeckList *getDeckList() const
     {
         return deck;

libcockatrice_network/libcockatrice/network/server/remote/game/server_game.cpp

@@ -32,6 +32,7 @@
 #include "server_spectator.h"
 
 #include <QDebug>
+#include <QElapsedTimer>
 #include <QRegularExpression>
 #include <QTimer>
 #include <google/protobuf/descriptor.h>
@@ -238,6 +239,17 @@ int Server_Game::getPlayerCount() const
     return participants.size() - getSpectatorCount();
 }
 
+int Server_Game::getCardsInGame() const
+{
+    QMutexLocker locker(&gameMutex);
+
+    int result = 0;
+    for (auto *player : getPlayers()) {
+        result += player->getCardCount();
+    }
+    return result;
+}
+
 int Server_Game::getSpectatorCount() const
 {
     QMutexLocker locker(&gameMutex);
@@ -330,6 +342,9 @@ void Server_Game::doStartGameIfReady(bool forceStartGame)
         }
     }
 
+    // Only actual starts are timed. The early returns above are no-ops.
+    QElapsedTimer startupTimer;
+    startupTimer.start();
     players = getPlayers(); // players could have been kicked, get new list of players
     if (lifecycleStrategy->onGameStarting(this) == Server_GameLifecycleStrategy::StartAction::Handled) {
         locker.unlock();
@@ -373,6 +388,7 @@ void Server_Game::doStartGameIfReady(bool forceStartGame)
 
     activePlayer = -1;
     nextTurn();
+    room->getServer()->observeGameStartDurationMs(startupTimer.nsecsElapsed() / 1000000);
 
     locker.unlock();
 

libcockatrice_network/libcockatrice/network/server/remote/game/server_game.h

@@ -123,6 +123,8 @@ public:
         return gameStarted;
     }
     int getPlayerCount() const;
+    /// Total cards across all players' zones. Takes gameMutex itself.
+    int getCardsInGame() const;
     int getSpectatorCount() const;
     QMap<int, Server_AbstractPlayer *> getPlayers() const;
     Server_AbstractPlayer *getPlayer(int id) const;

libcockatrice_network/libcockatrice/network/server/remote/server.h

@@ -180,6 +180,11 @@ public:
     {
         return false;
     }
+    /// Called once per actual game start with how long bringing every player's
+    /// zones online took, so servers can spot deck sizes that wedge threads.
+    virtual void observeGameStartDurationMs(qint64 /* elapsedMs */)
+    {
+    }
 
     Server_DatabaseInterface *getDatabaseInterface() const;
     int getNextLocalGameId()

libcockatrice_network/libcockatrice/network/server/remote/server_protocolhandler.h

@@ -136,7 +136,7 @@ public:
         return timeRunning - lastDataReceived;
     }
     bool addSaidMessageSize(int size);
-    void processCommandContainer(const CommandContainer &cont);
+    virtual void processCommandContainer(const CommandContainer &cont);
 
     void sendProtocolItem(const Response &item);
     void sendProtocolItem(const SessionEvent &item);