feat: readiness sentinel for Kubernetes

entrypoint.sh creates /home/agent/vol/.openclaw-initializing at startup
and removes it just before launching the gateway. Pod is not marked
ready until init (volume copy + config baking) is fully complete.

deployment.yaml adds readinessProbe: exec test ! -f sentinel,
with initialDelaySeconds=5, periodSeconds=5, failureThreshold=60
(5 minute window for slow storage on first deploy).

entrypoint.sh

@@ -61,6 +61,14 @@ export OPENCLAW_GATEWAY_PORT="${OPENCLAW_GATEWAY_PORT:-18800}"
 log()  { echo "[entrypoint] $*"; }
 warn() { echo "[entrypoint] WARNING: $*" >&2; }
 
+# ── Readiness sentinel ────────────────────────────────────────────
+# Present during init; deleted just before gateway starts.
+# Kubernetes readiness probe: test ! -f /home/agent/vol/.openclaw-initializing
+SENTINEL="${VOL}/.openclaw-initializing"
+mkdir -p "${VOL}"
+touch "${SENTINEL}"
+log "Readiness sentinel created at ${SENTINEL}"
+
 # ── Warn on missing required vars ────────────────────────────────
 for var in OPENCLAW_GATEWAY_TOKEN OPENCLAW_DEFAULT_MODEL OPENCLAW_AGENT_NAME \
            ANTHROPIC_API_KEY ANTHROPIC_MODEL ANTHROPIC_SMALL_FAST_MODEL PAI_AGENT_NAME; do
@@ -522,6 +530,8 @@ fi
 # Run gateway in background. OpenClaw manages its own internal restarts.
 # The sleep loop keeps the container alive if the gateway process exits.
 log "Starting OpenClaw gateway on port ${OPENCLAW_GATEWAY_PORT}..."
+rm -f "${SENTINEL}"
+log "Readiness sentinel removed — pod is ready."
 /home/agent/.npm-global/bin/openclaw gateway &
 
 while true; do