Add target player count stability QA gate

Docs/QA/MvpQaGates.md

@@ -251,3 +251,32 @@ Required evidence:
 
 This gate is both client and server relevant. It must be re-run for final
 milestone packages before sending an investor demo as stable.
+
+## Target Player Count Server Stability
+
+The target player count server stability gate proves the MVP server can hold
+the defined early test population long enough to exercise the core survival loop
+without a crash, disconnect cascade, or critical log spam.
+
+MVP target:
+
+- minimum proof: 2 players connected to the same server;
+- target closed-test smoke group: 4 players on one server;
+- stretch test: 8 players only after the dedicated/listen server path is
+  stable.
+
+Required evidence:
+
+- The server launch gate passes on the target host.
+- The two-client connection gate passes at minimum.
+- For closed-test readiness, repeat the same smoke with 4 connected clients.
+- During the run, connected clients exercise join, gather, craft/use fire,
+  craft/place shelter, survival pressure, disconnect, and reconnect where
+  possible.
+- Run the critical log scanner on the captured client and server logs.
+- Server-side UDP `7777` remains listening and the service remains active after
+  the smoke.
+
+This gate is server-relevant and should be re-run after every server package
+deployment that changes gameplay, persistence, networking, map content, or
+server startup behavior.