fix(python): preserve phrase semantics in sync queries (#3654)

## Summary

- serialize sync phrase queries consistently for execution and query
plans
- restore the documented no-argument hybrid `phrase_query()` behavior
- keep reranker input as the original user text without mutating the
builder

Fixes #3653.

## Testing

- `python/.venv/bin/python -m pytest <8 focused test nodes> -q` (`8
passed`)
- `python/.venv/bin/python -m ruff format --check
python/python/lancedb/query.py python/python/tests/test_fts.py
python/python/tests/test_hybrid_query.py`
- `python/.venv/bin/python -m ruff check .`
- `git diff --check origin/main...HEAD`

The complete hybrid module and the real native FTS phrase test were not
completed
in the current PyO3 runtime environment: both stalled in the native
`lancedb.connect()` fixture and were interrupted without an assertion
failure.

python/python/tests/test_fts.py

@@ -1084,6 +1084,84 @@ def test_fts_query_to_json():
     assert json_str == expected
 
 
+def test_fts_phrase_query_is_preserved_in_query_object():
+    query = LanceFtsQueryBuilder(mock.Mock(), "puppy runs").phrase_query()
+
+    query_object = query.to_query_object()
+
+    assert query_object.full_text_query.query == '"puppy runs"'
+
+
+def test_fts_phrase_query_execution_preserves_user_text():
+    table = mock.Mock()
+    table.schema = pa.schema([])
+    table._execute_query.return_value = pa.table({"text": ["result"]}).to_reader()
+
+    class CapturingReranker:
+        score = "relevance"
+
+        def __init__(self):
+            self.queries = []
+
+        def rerank_fts(self, query, results):
+            self.queries.append(query)
+            return results.append_column("_relevance_score", [[1.0]])
+
+    reranker = CapturingReranker()
+    query = (
+        LanceFtsQueryBuilder(table, "puppy runs")
+        .phrase_query()
+        .with_row_id(False)
+        .rerank(reranker)
+    )
+
+    query.to_arrow()
+
+    backend_query = table._execute_query.call_args.args[0]
+    assert (
+        backend_query.full_text_query.query,
+        reranker.queries,
+        query._query,
+    ) == ('"puppy runs"', ["puppy runs"], "puppy runs")
+
+
+def test_fts_phrase_query_false_preserves_string():
+    query = LanceFtsQueryBuilder(mock.Mock(), "puppy runs").phrase_query(False)
+
+    query_object = query.to_query_object()
+
+    assert query_object.full_text_query.query == "puppy runs"
+
+
+def test_fts_phrase_query_preserves_fully_quoted_string():
+    query = LanceFtsQueryBuilder(mock.Mock(), '"puppy runs"').phrase_query()
+
+    query_object = query.to_query_object()
+
+    assert query_object.full_text_query.query == '"puppy runs"'
+
+
+def test_fts_phrase_query_preserves_structured_phrase_query():
+    phrase_query = PhraseQuery("puppy runs", "text")
+    query = LanceFtsQueryBuilder(mock.Mock(), phrase_query).phrase_query()
+
+    query_object = query.to_query_object()
+
+    assert query_object.full_text_query.query == phrase_query
+
+
+def test_fts_phrase_query_rejects_other_structured_queries():
+    query = LanceFtsQueryBuilder(
+        mock.Mock(), MatchQuery("puppy", "text")
+    ).phrase_query()
+
+    with pytest.raises(
+        TypeError,
+        match=r"phrase_query\(\) requires a string or PhraseQuery, got MatchQuery",
+    ):
+        query.to_query_object()
+
+
 def test_fts_fast_search(table):
     table.create_fts_index("text")
 

python/python/tests/test_hybrid_query.py

@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright The LanceDB Authors
 
+from unittest import mock
+
 import lancedb
 
 from lancedb.query import LanceHybridQueryBuilder
@@ -191,6 +193,23 @@ async def test_analyze_plan(table: AsyncTable):
     assert "metrics=" in res
 
 
+def test_hybrid_phrase_query_is_preserved_in_analyze_plan():
+    table = mock.Mock()
+    analyzed_queries = []
+    table._analyze_plan.side_effect = lambda query: analyzed_queries.append(query) or ""
+
+    (
+        LanceHybridQueryBuilder(table)
+        .vector([0.1, 0.2])
+        .text("puppy runs")
+        .phrase_query()
+        .analyze_plan()
+    )
+
+    assert len(analyzed_queries) == 2
+    assert analyzed_queries[1].full_text_query.query == '"puppy runs"'
+
+
 @pytest.fixture
 def table_with_id(tmpdir_factory) -> Table:
     tmp_path = str(tmpdir_factory.mktemp("data"))