fix(python): preserve zero distance bounds in hybrid search (#3652)

## Summary

- preserve explicit `0.0` distance bounds in synchronous hybrid search
- distinguish omitted `None` endpoints from zero-valued endpoints when
configuring the vector child query
- add a public end-to-end regression test for a zero upper bound

## Testing

- `cd python && uv run --extra tests pytest
python/tests/test_hybrid_query.py -q`
- `uv run --project python ruff format --check
python/python/lancedb/query.py python/python/tests/test_hybrid_query.py`
- `uv run --project python ruff check .`

Fixes #3651

python/python/lancedb/query.py

@@ -2634,7 +2634,7 @@ class LanceHybridQueryBuilder(LanceQueryBuilder):
             self._vector_query.ef(self._ef)
         if self._bypass_vector_index:
             self._vector_query.bypass_vector_index()
-        if self._lower_bound or self._upper_bound:
+        if self._lower_bound is not None or self._upper_bound is not None:
             self._vector_query.distance_range(
                 lower_bound=self._lower_bound, upper_bound=self._upper_bound
             )

python/python/tests/test_hybrid_query.py

@@ -139,6 +139,20 @@ def test_hybrid_query_distance_range(sync_table: Table):
             assert 0.2 <= dist.as_py() <= 0.5
 
 
+def test_hybrid_query_applies_zero_upper_distance_bound(sync_table: Table):
+    result = (
+        sync_table.search(query_type="hybrid")
+        .vector([0.0, 0.4])
+        .text("elephant")
+        .distance_range(upper_bound=0.0)
+        .rerank(RRFReranker(return_score="all"))
+        .limit(4)
+        .to_arrow()
+    )
+
+    assert len(result) == 0
+
+
 @pytest.mark.asyncio
 async def test_hybrid_query_distance_range_async(table: AsyncTable):
     reranker = RRFReranker(return_score="all")