feat: make Mol explorer map-first

backend/app/api/routes/datasets.py

@@ -203,7 +203,7 @@ def select_vector_features(
         bbox=payload.bbox.model_dump(),
         limit=payload.limit,
     )
-    return envelope(VectorSelectionResponse(**result).model_dump())
+    return envelope(VectorSelectionResponse(**result).model_dump(exclude_none=True))
 
 
 @router.post("/datasets/{dataset_id}/vector/select/derive", status_code=201, response_model=dict)

backend/app/schemas/operations.py

@@ -220,6 +220,7 @@ class VectorSelectionDeriveRequest(VectorSelectionRequest):
 class VectorSelectionResponse(BaseModel):
     selection_bbox: VectorSelectionBBox
     feature_count: int
+    total_feature_count: int | None = None
     limit: int
     truncated: bool
     geojson: dict

backend/app/services/vector_feature_service.py

@@ -92,7 +92,7 @@ class VectorFeatureService:
         normalized_bbox = VectorFeatureService._normalize_selection_bbox(bbox)
         safe_limit = max(1, min(int(limit), 1000))
 
-        rows = (
+        query = (
             db.query(VectorFeature)
             .filter(VectorFeature.dataset_id == dataset_id)
             .filter(
@@ -107,17 +107,25 @@ class VectorFeatureService:
                     ),
                 )
             )
-            .order_by(VectorFeature.created_at.asc())
+        )
+        if hasattr(query, "count"):
+            total_feature_count = int(query.count())
+        else:  # Lightweight unit-test sessions do not always implement Query.count().
+            total_feature_count = len(query.all())
+
+        rows = (
+            query.order_by(VectorFeature.created_at.asc())
             .limit(safe_limit + 1)
             .all()
         )
-        truncated = len(rows) > safe_limit
+        truncated = total_feature_count > safe_limit
         selected_rows = rows[:safe_limit]
         features = [VectorFeatureService._row_to_geojson_feature(row) for row in selected_rows]
 
         return {
             "selection_bbox": normalized_bbox,
             "feature_count": len(features),
+            "total_feature_count": total_feature_count,
             "limit": safe_limit,
             "truncated": truncated,
             "geojson": {