fix: reuse local Java before downloading runtime

deploy/install.sh

@@ -89,13 +89,17 @@ download() {
   local url=$1 output=$2
   case "$url" in
     https://*)
-      curl --fail --silent --show-error --location --proto '=https' --proto-redir '=https' \
-        --tlsv1.2 "$url" -o "$output"
+      if ! curl --fail --silent --show-error --location --proto '=https' --proto-redir '=https' \
+        --tlsv1.2 --connect-timeout 15 --max-time 600 "$url" -o "$output"; then
+        die "Download failed: $url"
+      fi
       ;;
     *)
       [ "${KAIDI_ALLOW_INSECURE_UPDATE:-false}" = "true" ] || die "Release URLs must use HTTPS"
-      curl --fail --silent --show-error --location --proto '=http,https' \
-        --proto-redir '=http,https' "$url" -o "$output"
+      if ! curl --fail --silent --show-error --location --proto '=http,https' \
+        --proto-redir '=http,https' --connect-timeout 15 --max-time 600 "$url" -o "$output"; then
+        die "Download failed: $url"
+      fi
       ;;
   esac
 }
@@ -175,8 +179,40 @@ azul_arch() {
   esac
 }
 
+system_java_home() {
+  local java_bin resolved_java java_major home
+  if [ -n "${KAIDI_JAVA_HOME:-}" ]; then
+    home=${KAIDI_JAVA_HOME%/}
+    java_bin="$home/bin/java"
+  else
+    java_bin=$(command -v java 2>/dev/null || true)
+  fi
+  [ -x "$java_bin" ] || return 1
+  java_major=$(
+    "$java_bin" -version 2>&1 \
+      | sed -n 's/.*version "\([0-9][0-9]*\).*/\1/p' \
+      | head -n 1
+  )
+  [[ "$java_major" =~ ^[0-9]+$ ]] && [ "$java_major" -ge 17 ] || return 1
+  resolved_java=$(readlink -f "$java_bin" 2>/dev/null || printf '%s' "$java_bin")
+  case "$resolved_java" in
+    */bin/java) home=${resolved_java%/bin/java} ;;
+    *) return 1 ;;
+  esac
+  [ -x "$home/bin/java" ] || return 1
+  printf '%s\n' "$home"
+}
+
 prepare_java() {
-  local api java_metadata package_metadata package_uuid java_url java_sha256 actual_sha256
+  local api java_metadata package_metadata package_uuid java_url java_sha256 actual_sha256 system_home
+  if system_home=$(system_java_home); then
+    JAVA_STAGED_DIR="$WORK_DIR/java.next"
+    ln -s "$system_home" "$JAVA_STAGED_DIR"
+    log "Using existing Java 17 runtime at $system_home"
+    "$JAVA_STAGED_DIR/bin/java" -version
+    return
+  fi
+  log "No local Java 17 runtime found; downloading the official Azul Java 17 runtime"
   api="https://api.azul.com/metadata/v1/zulu/packages/?java_version=17&os=linux&arch=$(azul_arch)&archive_type=tar.gz&java_package_type=jre&release_status=ga&availability_types=CA&latest=true"
   java_metadata="$WORK_DIR/zulu-metadata.json"
   download "$api" "$java_metadata"