tests: centralize script path setup in conftest.py

Add a pytest-discovered tests/conftest.py for the last30days scripts path and
remove duplicate per-file sys.path.insert boilerplate from tests.

Normalize affected imports to rely on the shared scripts path and remove the
now-unneeded E402 suppressions.

tests/test_resolve.py

@@ -1,12 +1,8 @@
 import io
-import sys
 import unittest
 from contextlib import redirect_stderr
-from pathlib import Path
 from unittest.mock import patch
 
-sys.path.insert(0, str(Path(__file__).resolve().parents[1] / "skills" / "last30days" / "scripts"))
-
 from lib import resolve
 from lib.resolve import MAX_SUBS, _merge_category_peers
 
@@ -363,6 +359,5 @@ class AutoResolveCategoryIntegration(unittest.TestCase):
         result = resolve.auto_resolve("test topic", {})
         self.assertIsNone(result["category"])
 
-
 if __name__ == "__main__":
     unittest.main()