refactor(memory): keep session summaries structured

tests/agent/test_autocompact_unit.py

@@ -7,6 +7,7 @@ import pytest
 
 from nanobot.agent.autocompact import AutoCompact
 from nanobot.session.manager import Session, SessionManager
+from nanobot.session.summary import SessionSummary
 
 
 def _runtime(_session: Session | None = None):
@@ -176,29 +177,29 @@ class TestIsExpired:
 
 
 # ---------------------------------------------------------------------------
-# _format_summary
+# SessionSummary
 # ---------------------------------------------------------------------------
 
 
-class TestFormatSummary:
-    """Test AutoCompact._format_summary static method."""
+class TestSessionSummary:
+    """Test prompt rendering for the structured summary value."""
 
     def test_contains_isoformat_timestamp(self):
         """Output should contain last_active as isoformat."""
         last_active = datetime(2026, 5, 13, 14, 30, 0)
-        result = AutoCompact._format_summary("Some text", last_active)
+        result = SessionSummary("Some text", last_active).for_prompt()
         assert "2026-05-13T14:30:00" in result
 
     def test_contains_summary_text(self):
         """Output should contain the provided text verbatim."""
         last_active = datetime(2026, 1, 1)
-        result = AutoCompact._format_summary("User discussed Python.", last_active)
+        result = SessionSummary("User discussed Python.", last_active).for_prompt()
         assert "User discussed Python." in result
 
     def test_output_starts_with_label(self):
         """Output should start with the standard prefix."""
         last_active = datetime(2026, 1, 1)
-        result = AutoCompact._format_summary("text", last_active)
+        result = SessionSummary("text", last_active).for_prompt()
         assert result.startswith("Previous conversation summary (last active ")
 
 
@@ -498,7 +499,7 @@ class TestArchiveDelegates:
 
         entry = ac._summaries.get("cli:test")
         assert entry is not None
-        assert entry[0] == "Hello."
+        assert entry.text == "Hello."
 
     @pytest.mark.asyncio
     async def test_no_summary_when_compact_returns_empty(self):
@@ -577,21 +578,21 @@ class TestPrepareSession:
         ac = _make_autocompact()
         session = _make_session()
         last_active = datetime(2026, 5, 13, 14, 0, 0)
-        ac._summaries["cli:test"] = ("Hot summary.", last_active)
+        ac._summaries["cli:test"] = SessionSummary("Hot summary.", last_active)
 
         result_session, summary = ac.prepare_session(session, "cli:test")
 
         assert result_session is session
         assert summary is not None
-        assert "Hot summary." in summary
-        assert "Previous conversation summary" in summary
+        assert summary.text == "Hot summary."
+        assert "Previous conversation summary" in summary.for_prompt()
 
     def test_hot_path_pops_summary_one_shot(self):
         """Hot path should pop the summary (one-shot; second call returns None)."""
         ac = _make_autocompact()
         session = _make_session()
         last_active = datetime(2026, 1, 1)
-        ac._summaries["cli:test"] = ("One-shot.", last_active)
+        ac._summaries["cli:test"] = SessionSummary("One-shot.", last_active)
 
         _, summary1 = ac.prepare_session(session, "cli:test")
         assert summary1 is not None
@@ -614,7 +615,7 @@ class TestPrepareSession:
 
         assert result_session is session
         assert summary is not None
-        assert "Cold summary." in summary
+        assert summary.text == "Cold summary."
 
     def test_cold_path_tolerates_malformed_last_active(self):
         """A malformed persisted last_active must not raise on the turn path.
@@ -637,8 +638,8 @@ class TestPrepareSession:
 
         assert result_session is session
         assert summary is not None
-        assert "Cold summary." in summary
-        assert fallback.isoformat() in summary
+        assert summary.text == "Cold summary."
+        assert summary.last_active == fallback
 
     def test_cold_path_tolerates_missing_last_active(self):
         """A _last_summary dict without last_active must not raise."""
@@ -653,8 +654,8 @@ class TestPrepareSession:
 
         assert result_session is session
         assert summary is not None
-        assert "Cold summary." in summary
-        assert fallback.isoformat() in summary
+        assert summary.text == "Cold summary."
+        assert summary.last_active == fallback
 
     def test_cold_path_missing_text_returns_none(self):
         """A _last_summary without a non-empty string text yields no summary."""
@@ -685,7 +686,10 @@ class TestPrepareSession:
         ac.sessions = mock_sm
         key = "dream:20260602-155256"
         ac._archiving.add(key)
-        ac._summaries[key] = ("Hot summary.", datetime(2026, 6, 2, 15, 52, 56))
+        ac._summaries[key] = SessionSummary(
+            "Hot summary.",
+            datetime(2026, 6, 2, 15, 52, 56),
+        )
         session = _make_session(
             key=key,
             updated_at=datetime.now() - timedelta(minutes=20),
@@ -725,8 +729,9 @@ class TestPrepareSession:
             },
         })
         last_active = datetime(2026, 5, 13, 14, 0, 0)
-        ac._summaries["cli:test"] = ("Hot summary.", last_active)
+        ac._summaries["cli:test"] = SessionSummary("Hot summary.", last_active)
 
         _, summary = ac.prepare_session(session, "cli:test")
-        assert "Hot summary." in summary
+        assert summary is not None
+        assert summary.text == "Hot summary."
         # After hot path pops, cold path would kick in on next call