Add platform-specific query optimizations

- hackernews: use extract_core_subject instead of raw topic, add
  points>5 filter and restrictSearchableAttributes=title to reduce
  noise from URL-match and low-signal posts
- youtube: add --dateafter parameter to yt-dlp for server-side date
  filtering (Python soft filter still handles fallback)
- reddit: skip opinion/review query variant for how_to/comparison
  queries where it adds noise
- bird_x: add OR-group retry with compound terms before falling back
  to word-dropping (uses X OR operator for multi-concept queries)
- query.py: add detect_query_type() and extract_compound_terms()

scripts/lib/bird_x.py

@@ -237,8 +237,20 @@ def search_x(
     # Check if we got results
     items = parse_bird_response(response, query=core_topic)
 
-    # Retry with fewer keywords if 0 results and query has 3+ words
+    # Retry with OR groups for multi-word queries (X supports OR operator)
     core_words = core_topic.split()
+    if not items and len(core_words) >= 2:
+        from .query import extract_compound_terms
+        compounds = extract_compound_terms(topic)
+        if compounds:
+            # Build OR-group query: ("multi-agent" OR "agent simulation") since:DATE
+            or_parts = ' OR '.join(f'"{t}"' for t in compounds[:3])
+            _log(f"0 results for '{core_topic}', retrying with OR groups: {or_parts}")
+            query = f"({or_parts}) since:{from_date}"
+            response = _run_bird_search(query, count, timeout)
+            items = parse_bird_response(response, query=core_topic)
+
+    # Retry with fewer keywords if still 0 results and query has 3+ words
     if not items and len(core_words) > 2:
         shorter = ' '.join(core_words[:2])
         _log(f"0 results for '{core_topic}', retrying with '{shorter}'")