feat(server): list_sessions 支持 project 过滤（json_extract + Python 兜底）

tests/test_server_store.py

@@ -213,3 +213,24 @@ def test_projects_upsert_empty_name_rejected(projects_store, tmp_path):
     with pytest.raises(ProjectConfigError):
         projects_store.upsert(name="", display_name="P", template="", write_instruction="",
                               rules=[], existing_system_code_dir="", design_docs_dir="")
+
+def test_list_sessions_filter_by_project(store):
+    a = store.create_session("u1", name="A", project="stock")
+    b = store.create_session("u1", name="B", project="other")
+    recs = store.list_sessions("u1", project="stock")
+    ids = {r.session_id for r in recs}
+    assert a.session_id in ids and b.session_id not in ids
+
+
+def test_list_sessions_filter_empty_project(store):
+    e = store.create_session("u1", name="E")
+    store.create_session("u1", name="X", project="stock")
+    recs = store.list_sessions("u1", project="")
+    assert all(r.project == "" for r in recs)
+    assert e.session_id in {r.session_id for r in recs}
+
+
+def test_list_sessions_no_project_returns_all(store):
+    store.create_session("u1", name="A", project="stock")
+    store.create_session("u1", name="B", project="other")
+    assert len(store.list_sessions("u1")) == 2