fix(infra): fix sequential phase gap + add phase 7 guards

1. last_completed_phase now stops at first gap — prevents --resume from
   skipping phases when --phase=N created non-sequential markers
2. Phase 7 fails early if .env.ecosystem is missing (points to --phase=6)
3. Warns if compose config JSON cache fails — graceful degradation

docs/devops/single_azure_vm/setup.sh

@@ -99,7 +99,8 @@ is_phase_done() {
 last_completed_phase() {
   local last=0
   for i in 1 2 3 4 5 6 7 8; do
-    is_phase_done "$i" && last=$i
+    # Stop at first gap — phases must be sequential
+    is_phase_done "$i" && last=$i || break
   done
   echo "$last"
 }
@@ -564,6 +565,11 @@ phase7_deploy() {
   setup_compose_env
 
   local plat_dir="${INSTALL_DIR}/learning_ai_common_plat"
+
+  # Guard: .env.ecosystem must exist (created by phase 6)
+  if [ ! -f "${plat_dir}/.env.ecosystem" ]; then
+    fail "Missing ${plat_dir}/.env.ecosystem — run phase 6 first: sudo ./setup.sh --phase=6"
+  fi
   local build_ok=() build_fail=() build_skip=()
   mkdir -p "${STATE_DIR}/builds"
 
@@ -580,6 +586,11 @@ phase7_deploy() {
   compose_json=$(docker compose -f "${plat_dir}/${COMPOSE_FILE}" \
     --env-file "${plat_dir}/.env.ecosystem" config --format json 2>/dev/null || true)
 
+  if [ -z "$compose_json" ]; then
+    warn "  Could not parse compose config (docker compose config --format json failed)."
+    warn "  Per-service build detection disabled — all services will attempt to build."
+  fi
+
   for svc in "${all_services[@]}"; do
     idx=$((idx + 1))