Tighten relevance scoring and Polymarket ranking

Score against original user intent on Reddit, remove the artificial low-end relevance floor, and make Polymarket semantics dominate generic market quality signals.

Also apply the relevance filter to Polymarket and update the affected cross-source tests.

Validation: uv run python -m unittest

tests/test_relevance.py

@@ -75,7 +75,7 @@ class TestTokenOverlapRelevance(unittest.TestCase):
 
     def test_floor_at_0_1(self):
         rel = token_overlap_relevance("quantum physics", "cat dancing video")
-        self.assertGreaterEqual(rel, 0.1)
+        self.assertEqual(rel, 0.0)
 
     def test_full_match_returns_1(self):
         rel = token_overlap_relevance("python tutorial", "Python Tutorial for Beginners")
@@ -96,6 +96,15 @@ class TestTokenOverlapRelevance(unittest.TestCase):
         rel = token_overlap_relevance("the a is", "some content here")
         self.assertEqual(rel, 0.5)
 
+    def test_generic_only_overlap_stays_below_filter_threshold(self):
+        rel = token_overlap_relevance("anthropic odds", "Republican house odds update")
+        self.assertLess(rel, 0.3)
+
+    def test_informative_partial_match_stays_above_generic_only(self):
+        generic_only = token_overlap_relevance("anthropic odds", "Republican house odds update")
+        informative = token_overlap_relevance("anthropic odds", "Anthropic valuation market")
+        self.assertGreater(informative, generic_only)
+
 
 class TestHashtagRelevance(unittest.TestCase):
     """Tests for hashtag-aware relevance (TikTok/Instagram pattern)."""