Extract relevance_filter, add Bluesky/TruthSocial type hint + test coverage

- Extract _relevance_filter from last30days.py closure to score.relevance_filter()
  for testability
- Add BlueskyItem/TruthSocialItem to sort_items() type hint (was missing despite
  being in _ITEM_SOURCE_MAP)
- Add tests: Bluesky/TruthSocial engagement scoring, sort_items mixed sources,
  relevance_filter behavior (threshold, minimum-result guarantee, missing attr),
  select_openai_model HTTP 401/403 error paths

scripts/last30days.py

@@ -1830,27 +1830,14 @@ def main():
     deduped_web = websearch.dedupe_websearch(sorted_web) if sorted_web else []
 
     # Post-retrieval relevance filter: drop low-relevance items per source
-    # Only filter when there are enough items (>3) to avoid empty results
-    def _relevance_filter(items, source_name, threshold=0.3):
-        """Filter items below relevance threshold with minimum-result guarantee."""
-        if len(items) <= 3:
-            return items
-        passed = [i for i in items if getattr(i, 'relevance', 0.0) >= threshold]
-        if not passed:
-            # Keep top 3 by relevance if all filtered
-            print(f"[{source_name} WARNING] All results below relevance {threshold}, keeping top 3", file=sys.stderr)
-            by_rel = sorted(items, key=lambda x: getattr(x, 'relevance', 0.0), reverse=True)
-            return by_rel[:3]
-        return passed
-
-    deduped_reddit = _relevance_filter(deduped_reddit, "REDDIT")
-    deduped_x = _relevance_filter(deduped_x, "X")
-    deduped_youtube = _relevance_filter(deduped_youtube, "YOUTUBE")
-    deduped_tiktok = _relevance_filter(deduped_tiktok, "TIKTOK")
-    deduped_ig = _relevance_filter(deduped_ig, "INSTAGRAM")
-    deduped_hn = _relevance_filter(deduped_hn, "HN")
-    deduped_bsky = _relevance_filter(deduped_bsky, "BLUESKY")
-    deduped_ts = _relevance_filter(deduped_ts, "TRUTHSOCIAL")
+    deduped_reddit = score.relevance_filter(deduped_reddit, "REDDIT")
+    deduped_x = score.relevance_filter(deduped_x, "X")
+    deduped_youtube = score.relevance_filter(deduped_youtube, "YOUTUBE")
+    deduped_tiktok = score.relevance_filter(deduped_tiktok, "TIKTOK")
+    deduped_ig = score.relevance_filter(deduped_ig, "INSTAGRAM")
+    deduped_hn = score.relevance_filter(deduped_hn, "HN")
+    deduped_bsky = score.relevance_filter(deduped_bsky, "BLUESKY")
+    deduped_ts = score.relevance_filter(deduped_ts, "TRUTHSOCIAL")
 
     # Cross-source linking: annotate items that discuss the same story
     dedupe.cross_source_link(