fix: correct integration test assertions for semantic search

- test_search_by_content: format_search_result() does not include
  body_text, so check for the expected message_id instead.
- test_search_no_results: vector cosine similarity always returns
  nearest neighbors; use a date filter far in the future to
  guarantee zero results instead.

tests/test_integration.py

@@ -132,11 +132,17 @@ def qdrant_setup():
 
 class TestSearchEmails:
     def test_search_by_content(self, qdrant_setup):
-        """Search for emails about Python/programming."""
+        """Semantic search returns the most relevant email first.
+
+        Searching for 'Python programming' should match email 001
+        which discusses Python and vector databases.
+        """
         result = search_emails(query="Python programming")
         assert result["count"] >= 1
         assert "results" in result
-        assert any("Python" in r.get("body_text", "") for r in result["results"])
+        # The top result should be email 001 (most semantically relevant)
+        messages = [r["message_id"] for r in result["results"]]
+        assert "<test-001@example.com>" in messages
 
     def test_search_with_participant_filter(self, qdrant_setup):
         """Search emails sent by alice."""
@@ -153,9 +159,17 @@ class TestSearchEmails:
             date = r.get("date", "")
             assert date >= "2026-02-01"
 
-    def test_search_no_results(self, qdrant_setup):
-        """Search for something that doesn't exist."""
-        result = search_emails(query="gobbledygookxyz123")
+    def test_search_no_results_by_date(self, qdrant_setup):
+        """Search with a filter that matches no emails returns empty results.
+
+        With semantic (vector) search, any text query always has nearest
+        neighbors, so we use a date filter that matches nothing instead.
+        """
+        result = search_emails(
+            query="anything",
+            start_date="2099-01-01",
+            end_date="2099-12-31",
+        )
         assert result["count"] == 0
         assert result["results"] == []