test: 300접속 capacity calibration을 재현 가능하게 구성

비밀값 자동 준비, 4 CPU/8GiB API launcher, fixture 검증 기반 calibration config를 추가한다. tRPC v11 GET input encoding 오류를 고치고 300 SSE/HTTP 실제 실행 절차를 문서화한다.

tools/load-tests/scripts/run-capacity-api.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+set -eu
+
+workspace_root=$(CDPATH= cd -- "$(dirname -- "$0")/../../.." && pwd)
+secret_env="$workspace_root/tools/load-tests/secrets/capacity.env"
+
+if [ ! -f "$secret_env" ]; then
+    echo "capacity.env is missing; run the load-test prepare command first" >&2
+    exit 1
+fi
+
+secret_mode=$(stat -c '%a' "$secret_env")
+if [ "$secret_mode" != "600" ]; then
+    echo "capacity.env must have mode 0600" >&2
+    exit 1
+fi
+
+set -a
+# shellcheck disable=SC1090
+. "$secret_env"
+set +a
+
+export GAME_API_ROLE=server
+cd "$workspace_root"
+exec taskset -c "${CAPACITY_CPUSET:-0-3}" "${CAPACITY_NODE_BINARY:-node}" app/game-api/dist/index.js