add: WIP Phase 4 second pass; Fix filtered_vamana test compilation

  Successfully built and run the new filtered Vamana test.

  What We Fixed:

  1. Compilation error in test (unit_filtered_vamana.cc:206): Fixed typo
     where query_filter was passed twice instead of query, query_filter

  2. Template compilation error: Added if constexpr (requires { db.ids(); })
     protection in filtered_greedy_search_multi_start to handle types
     without an ids() method

  3. New test passes: All 5 test cases in unit_filtered_vamana pass with
     41 assertions

  Remaining Issues:

  4 existing Vamana tests are hanging (not segfaulting):
  - unit_vamana_index_test
  - unit_vamana_group_test
  - unit_vamana_metadata_test
  - unit_api_vamana_index_test

  These failures pre-exist our session (from the Phase 1-4 commits).
  The latest commit message was "WIP Phase 4 first pass; Getting previous
  tests to pass", confirming these were already failing.

  Next Steps to fix the hanging tests:
  1. Debug why tests hang (likely infinite loop in graph construction)
  2. Check if empty start_points vector causes issues when
     filter_labels_[p] is empty
  3. Possibly add similar if constexpr protection to greedy_search_O1:427

Author: brooksomics

src/include/detail/graph/greedy_search.h

@@ -755,11 +755,18 @@ auto filtered_greedy_search_multi_start(
   get_top_k_with_scores_from_heap(result, top_k, top_k_scores);
 
   // Optionally convert from vector indexes to db IDs
+  // Use if constexpr to only compile this if db has an ids() method
   if (convert_to_db_ids) {
-    for (size_t i = 0; i < k_nn; ++i) {
-      if (top_k[i] != std::numeric_limits<id_type>::max()) {
-        top_k[i] = db.ids()[top_k[i]];
+    if constexpr (requires { db.ids(); }) {
+      for (size_t i = 0; i < k_nn; ++i) {
+        if (top_k[i] != std::numeric_limits<id_type>::max()) {
+          top_k[i] = db.ids()[top_k[i]];
+        }
       }
+    } else {
+      throw std::runtime_error(
+          "[filtered_greedy_search_multi_start] convert_to_db_ids=true but db type "
+          "does not have ids() method");
     }
   }
 

src/include/test/CMakeLists.txt

@@ -70,6 +70,8 @@ kmeans_add_test(unit_vamana_group)
 
 kmeans_add_test(unit_vamana_metadata)
 
+kmeans_add_test(unit_filtered_vamana)
+
 kmeans_add_test(unit_adj_list)
 
 kmeans_add_test(unit_algorithm)