chore: remove unused lib/discovery crate (#5266)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

lib/discovery/src/systems/validation.rs

-// SPDX-FileCopyrightText: Copyright (c) 2024-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
-// SPDX-License-Identifier: Apache-2.0
-
-//! Shared validation helpers for discovery system configuration.
-
-use validator::ValidationError;
-
-/// Validate that a cluster identifier is non-empty and free of surrounding whitespace.
-pub(crate) fn validate_cluster_id(cluster_id: &str) -> Result<(), ValidationError> {
-    if cluster_id.trim().is_empty() {
-        let mut err = ValidationError::new("cluster_id_empty");
-        err.add_param("value".into(), &cluster_id);
-        return Err(err);
-    }
-
-    // Reject cluster IDs with leading or trailing whitespace
-    if cluster_id.trim() != cluster_id {
-        let mut err = ValidationError::new("cluster_id_has_whitespace");
-        err.add_param("value".into(), &cluster_id);
-        return Err(err);
-    }
-
-    Ok(())
-}