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_footer_nudge_suppression.py

@@ -1,4 +1,3 @@
-# ruff: noqa: E402
 """Tests for the BRAVE/SERPER web-promo suppression when hosting-model-driven."""
 
 from __future__ import annotations
@@ -11,7 +10,6 @@ import unittest
 from pathlib import Path
 
 REPO_ROOT = Path(__file__).resolve().parents[1]
-sys.path.insert(0, str(REPO_ROOT / "skills" / "last30days" / "scripts"))
 
 
 def _engine() -> Path:
@@ -90,6 +88,5 @@ class FooterNudgeSuppressionTests(unittest.TestCase):
             msg="web promo should be suppressed when --plan is passed",
         )
 
-
 if __name__ == "__main__":
     unittest.main()