test: speed up CI and harden the suite

tests/utils/test_abbreviate_path.py

@@ -1,6 +1,7 @@
 """Tests for abbreviate_path utility."""
 
 import os
+
 from nanobot.utils.path import abbreviate_path
 
 
@@ -9,7 +10,6 @@ class TestAbbreviatePathShort:
         assert abbreviate_path("/home/user/file.py") == "/home/user/file.py"
 
     def test_exact_max_len_unchanged(self):
-        path = "/a/b/c"  # 7 chars
         assert abbreviate_path("/a/b/c", max_len=7) == "/a/b/c"
 
     def test_basename_only(self):

tests/utils/test_searchusage.py

@@ -2,16 +2,16 @@
 
 from __future__ import annotations
 
-import pytest
 from unittest.mock import AsyncMock, MagicMock, patch
 
+import pytest
+
+from nanobot.utils.helpers import build_status_content
 from nanobot.utils.searchusage import (
     SearchUsageInfo,
     _parse_tavily_usage,
     fetch_search_usage,
 )
-from nanobot.utils.helpers import build_status_content
-
 
 # ---------------------------------------------------------------------------
 # SearchUsageInfo.format() tests