feat(corroboration): halacha matcher + cosine threshold (INV-COR3, X11)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

mcp-server/tests/test_corroboration.py

@@ -15,3 +15,12 @@ def test_treatment_polarity():
     assert cor.is_positive("followed") and cor.is_positive("explained")
     assert cor.is_negative("distinguished") and cor.is_negative("overruled")
     assert not cor.is_positive("mentioned") and not cor.is_negative("mentioned")
+
+def test_match_accepts_above_threshold():
+    assert cor.accept_match(("h1", 0.62), floor=0.50) == "h1"
+
+def test_match_rejects_below_threshold():
+    assert cor.accept_match(("h1", 0.41), floor=0.50) is None
+
+def test_match_rejects_empty():
+    assert cor.accept_match(None, floor=0.50) is None