style(bench): gate the rerank-sweep flag and helper on the embeddings feature

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

crates/clawhdf5-bench/src/bin/longmemeval_bench.rs

@@ -107,6 +107,7 @@ impl Mode {
         }
     }
 
+    #[cfg_attr(not(feature = "embeddings"), allow(dead_code))]
     fn reranked(mut self, label: &'static str, rerank: ReRankConfig) -> Self {
         self.label = label;
         self.rerank = Some(rerank);
@@ -929,6 +930,7 @@ fn main() {
     let mut limit: Option<usize> = None;
     let mut weights_dir: Option<String> = None;
     let mut sweep = false;
+    #[cfg_attr(not(feature = "embeddings"), allow(unused_mut, unused_variables))]
     let mut rerank_sweep = false;
     let mut args = std::env::args().skip(1);
     while let Some(arg) = args.next() {
@@ -938,7 +940,16 @@ fn main() {
                 limit = Some(v.parse().expect("--limit must be a positive integer"));
             }
             "--sweep" => sweep = true,
-            "--rerank-sweep" => rerank_sweep = true,
+            "--rerank-sweep" => {
+                // Re-ranking needs the vector stage to have candidates worth
+                // reordering, so this is an embeddings-only comparison.
+                #[cfg(feature = "embeddings")]
+                {
+                    rerank_sweep = true;
+                }
+                #[cfg(not(feature = "embeddings"))]
+                eprintln!("warning: --rerank-sweep needs --features embeddings; ignoring");
+            }
             "--embeddings" => {
                 weights_dir = Some(args.next().expect("--embeddings needs a directory"));
             }