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_save_raw_per_entity.py

@@ -1,4 +1,3 @@
-# ruff: noqa: E402
 """Tests for per-entity save files when running vs-mode or --competitors.
 
 Each entity's sub-run produces its own {entity-slug}-raw.md. Single-entity
@@ -15,7 +14,6 @@ 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() -> Path:
@@ -79,6 +77,5 @@ class PerEntitySaveFilesTests(unittest.TestCase):
         self.assertIn("## Resolved Entities", content)
         self.assertIn("**Anthropic**", content)
 
-
 if __name__ == "__main__":
     unittest.main()