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_competitors_resolve_integration.py

@@ -1,4 +1,3 @@
-# ruff: noqa: E402
 """Integration tests for per-entity Step 0.55 resolution inside competitor fan-out."""
 
 from __future__ import annotations
@@ -7,12 +6,8 @@ import io
 import sys
 import unittest
 from contextlib import redirect_stderr
-from pathlib import Path
 from unittest import mock
 
-REPO_ROOT = Path(__file__).resolve().parents[1]
-sys.path.insert(0, str(REPO_ROOT / "skills" / "last30days" / "scripts"))
-
 
 def _fake_report(topic: str):
     """Minimal Report stand-in for runner return values."""
@@ -326,6 +321,5 @@ class PerEntityResolveTests(unittest.TestCase):
 
         return [runner(c) for c in competitors]
 
-
 if __name__ == "__main__":
     unittest.main()