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_reddit_enrich.py

@@ -1,12 +1,10 @@
 """Tests for reddit_enrich.py — comment enrichment and parsing."""
 
 import json
-import sys
 import unittest
 from pathlib import Path
 
 # Add lib to path
-sys.path.insert(0, str(Path(__file__).parent.parent / "skills" / "last30days" / "scripts"))
 
 from lib import reddit_enrich
 
@@ -124,6 +122,5 @@ class TestExtractCommentInsights(unittest.TestCase):
         insights = reddit_enrich.extract_comment_insights(comments, limit=3)
         self.assertLessEqual(len(insights), 3)
 
-
 if __name__ == "__main__":
     unittest.main()