test: add multi-word query tests for truncation match strategy

Tests phrase matching, proximity co-occurrence, and sliding window
coverage maximisation — the three new tiers from the truncation fix.

tests/tools/test_session_search.py

@@ -146,6 +146,40 @@ class TestTruncateAroundMatches:
         result = _truncate_around_matches(text, "KEYWORD")
         assert "KEYWORD" in result
 
+    def test_multiword_phrase_match_beats_individual_term(self):
+        """Full phrase deep in text should be found even when a single term
+        appears much earlier in boilerplate."""
+        boilerplate = "The project setup is complex. " * 500  # ~15K, has 'project' early
+        filler = "x" * (MAX_SESSION_CHARS + 20000)
+        target = "We reviewed the keystone project roadmap in detail."
+        text = boilerplate + filler + target + filler
+        result = _truncate_around_matches(text, "keystone project")
+        assert "keystone project" in result.lower()
+
+    def test_multiword_proximity_cooccurrence(self):
+        """When exact phrase is absent, terms co-occurring within proximity
+        should be preferred over a lone early term."""
+        early = "project " + "a" * (MAX_SESSION_CHARS + 20000)
+        # Place 'keystone' and 'project' near each other (but not as exact phrase)
+        cooccur = "this keystone initiative for the project was pivotal"
+        tail = "b" * (MAX_SESSION_CHARS + 20000)
+        text = early + cooccur + tail
+        result = _truncate_around_matches(text, "keystone project")
+        assert "keystone" in result.lower()
+        assert "project" in result.lower()
+
+    def test_multiword_window_maximises_coverage(self):
+        """Sliding window should capture as many match clusters as possible."""
+        # Place two phrase matches: one at ~50K, one at ~60K, both should fit
+        pre = "z" * 50000
+        match1 = " alpha beta "
+        gap = "z" * 10000
+        match2 = " alpha beta "
+        post = "z" * (MAX_SESSION_CHARS + 40000)
+        text = pre + match1 + gap + match2 + post
+        result = _truncate_around_matches(text, "alpha beta")
+        assert result.lower().count("alpha beta") == 2
+
 
 # =========================================================================
 # session_search (dispatcher)