docs(search): note why reindex test references db crate migrations

crates/search/tests/reindex.rs

@@ -16,6 +16,8 @@ fn unique_index() -> String {
     format!("reindex_test_{}", uuid::Uuid::new_v4().simple())
 }
 
+// Path is relative to this crate's root; the schema lives in the `db` crate.
+// If the workspace layout changes, update this path.
 #[sqlx::test(migrations = "../db/migrations")]
 async fn reindex_resolves_term_labels_and_finds_by_label(pool: PgPool) {
     let db = Db::from_pool(pool);