refactor(replication): move resync classifiers into crate (#4170)

crates/replication/src/runtime.rs

@@ -82,6 +82,14 @@ pub fn resized_worker_counts(
     }
 }
 
+pub fn mrf_worker_size_to_count(size: i32) -> usize {
+    let non_negative = size.max(0);
+    match usize::try_from(non_negative) {
+        Ok(size) => size,
+        Err(_) => 0,
+    }
+}
+
 pub fn worker_counts_for_priority(
     priority: &ReplicationPriority,
     current_workers: usize,
@@ -189,6 +197,13 @@ mod tests {
         );
     }
 
+    #[test]
+    fn mrf_worker_size_to_count_clamps_negative_values() {
+        assert_eq!(mrf_worker_size_to_count(-1), 0);
+        assert_eq!(mrf_worker_size_to_count(0), 0);
+        assert_eq!(mrf_worker_size_to_count(3), 3);
+    }
+
     #[test]
     fn auto_priority_grows_toward_defaults() {
         assert_eq!(