test: tidy embedding follow-up imports

Agent-Logs-Url: https://github.com/MemPalace/mempalace/sessions/3213a67a-6871-4bb2-9ae0-23fa11001a22

Co-authored-by: igorls <4753812+igorls@users.noreply.github.com>

tests/test_convo_miner_unit.py

@@ -1,5 +1,7 @@
 """Unit tests for convo_miner pure functions (no chromadb needed)."""
 
+import contextlib
+
 from mempalace.convo_miner import (
     _file_chunks_locked,
     chunk_exchanges,
@@ -116,8 +118,6 @@ class TestScanConvos:
 
 class TestFileChunksLocked:
     def test_uses_bounded_upsert_batches(self, monkeypatch):
-        import contextlib
-
         import mempalace.convo_miner as convo_miner
 
         class FakeCol:

tests/test_embedding.py

@@ -1,5 +1,3 @@
-import builtins
-
 import pytest
 
 import mempalace.embedding as embedding
@@ -62,6 +60,8 @@ def test_unknown_device_warns_once(monkeypatch, caplog):
 
 
 def test_onnxruntime_import_error_falls_back_to_cpu(monkeypatch):
+    import builtins
+
     real_import = builtins.__import__
 
     def fake_import(name, *args, **kwargs):