fix(engine): add debug logging when lookup returns empty

When lookup cannot find the requested resource (apierrors.IsNotFound),
add slog.Debug() calls with structured fields (apiVersion, kind,
namespace, name) so that users running helm template --debug can see
why lookup returned an empty map instead of silently swallowing the
not-found result.

Fixes: https://github.com/helm/helm/issues/32101
Signed-off-by: Ogulcan Aydogan <ogulcanaydogan@hotmail.com>

pkg/engine/lookup_func.go

@@ -73,6 +73,12 @@ func newLookupFunction(clientProvider ClientProvider) lookupFunc {
 				if apierrors.IsNotFound(err) {
 					// Just return an empty interface when the object was not found.
 					// That way, users can use `if not (lookup ...)` in their templates.
+					slog.Debug("lookup: resource not found",
+						slog.String("apiVersion", apiversion),
+						slog.String("kind", kind),
+						slog.String("namespace", namespace),
+						slog.String("name", name),
+					)
 					return map[string]any{}, nil
 				}
 				return map[string]any{}, err
@@ -85,6 +91,11 @@ func newLookupFunction(clientProvider ClientProvider) lookupFunc {
 			if apierrors.IsNotFound(err) {
 				// Just return an empty interface when the object was not found.
 				// That way, users can use `if not (lookup ...)` in their templates.
+				slog.Debug("lookup: resource list not found",
+					slog.String("apiVersion", apiversion),
+					slog.String("kind", kind),
+					slog.String("namespace", namespace),
+				)
 				return map[string]any{}, nil
 			}
 			return map[string]any{}, err