Fix ssh-keygen overwrite prompt and key landing in root home

mktemp creates the file before ssh-keygen runs — keygen sees it exists
and prompts. Switch to mktemp -d so keygen writes a fresh file.

When run via sudo SUDO_USER is set but HOME=/root. Resolve the real
home via getent so the key lands in the operator's ~/.ssh, not root's.

operator_setup.sh

@@ -515,11 +515,12 @@ SSH_DIR="${MOUNT_POINT}/root/.ssh"
 mkdir -p "$SSH_DIR"
 
 if [[ "$SSH_MODE" == "generate" ]]; then
-    TMP_KEY=$(mktemp)
+    TMP_DIR=$(mktemp -d)
+    TMP_KEY="${TMP_DIR}/id_ed25519"
     ssh-keygen -t ed25519 -N "" -C "" -f "$TMP_KEY" -q
     PRIVKEY=$(cat "$TMP_KEY")
     PUBKEY=$(cat "${TMP_KEY}.pub")
-    rm -f "$TMP_KEY" "${TMP_KEY}.pub"
+    rm -rf "$TMP_DIR"
 
     echo "$PUBKEY" > "${SSH_DIR}/authorized_keys"
 
@@ -533,12 +534,14 @@ if [[ "$SSH_MODE" == "generate" ]]; then
         echo "---"
     fi
 
-    # Save locally to ~/.ssh/bb-<device_id>
-    LOCAL_KEY_DIR="$HOME/.ssh"
+    # Save to the invoking user's ~/.ssh (SUDO_USER if running via sudo, else HOME)
+    REAL_HOME=$(getent passwd "${SUDO_USER:-$USER}" 2>/dev/null | cut -d: -f6)
+    LOCAL_KEY_DIR="${REAL_HOME:-$HOME}/.ssh"
     LOCAL_KEY_PATH="${LOCAL_KEY_DIR}/bb-${DEVICE_ID}"
     mkdir -p "$LOCAL_KEY_DIR"
     echo "$PRIVKEY" > "$LOCAL_KEY_PATH"
     chmod 600 "$LOCAL_KEY_PATH"
+    [[ -n "$SUDO_USER" ]] && chown "$SUDO_USER" "$LOCAL_KEY_PATH" || true
     info "Private key saved locally: ${LOCAL_KEY_PATH}"
 
     unset PRIVKEY