fix(session_search): order recent mode by last activity instead of start time

- order session_search recent-mode results by last activity instead of session start time
- add an opt-in `order_by_last_active` path to `SessionDB.list_sessions_rich`
- add regression coverage for both the database ordering and recent-mode call path

tests/test_hermes_state.py

@@ -1719,6 +1719,39 @@ class TestListSessionsRich:
         # No messages, so last_active falls back to started_at
         assert sessions[0]["last_active"] == sessions[0]["started_at"]
 
+    def test_order_by_last_active_surfaces_recently_touched_older_session_first(self, db):
+        t0 = 1709500000.0
+        db.create_session("old", "cli")
+        db.create_session("new", "cli")
+
+        with db._lock:
+            db._conn.execute("UPDATE sessions SET started_at=? WHERE id=?", (t0, "old"))
+            db._conn.execute("UPDATE sessions SET started_at=? WHERE id=?", (t0 + 10, "new"))
+
+        db.append_message("old", "user", "old first")
+        db.append_message("new", "user", "new first")
+        db.append_message("old", "assistant", "old touched later")
+
+        with db._lock:
+            db._conn.execute(
+                "UPDATE messages SET timestamp=? WHERE session_id=? AND role=? AND content=?",
+                (t0 + 1, "old", "user", "old first"),
+            )
+            db._conn.execute(
+                "UPDATE messages SET timestamp=? WHERE session_id=? AND role=? AND content=?",
+                (t0 + 11, "new", "user", "new first"),
+            )
+            db._conn.execute(
+                "UPDATE messages SET timestamp=? WHERE session_id=? AND role=? AND content=?",
+                (t0 + 20, "old", "assistant", "old touched later"),
+            )
+            db._conn.commit()
+
+        assert [s["id"] for s in db.list_sessions_rich(limit=5)] == ["new", "old"]
+        assert [
+            s["id"] for s in db.list_sessions_rich(limit=5, order_by_last_active=True)
+        ] == ["old", "new"]
+
     def test_rich_list_includes_title(self, db):
         db.create_session("s1", "cli")
         db.set_session_title("s1", "refactoring auth")

tests/tools/test_session_search.py

@@ -242,6 +242,21 @@ class TestSessionSearchConcurrency:
 
 
 class TestRecentSessionListing:
+    def test_recent_mode_requests_last_active_ordering(self):
+        from unittest.mock import MagicMock
+
+        mock_db = MagicMock()
+        mock_db.list_sessions_rich.return_value = []
+
+        result = json.loads(_list_recent_sessions(mock_db, limit=5))
+
+        assert result["success"] is True
+        mock_db.list_sessions_rich.assert_called_once_with(
+            limit=10,
+            exclude_sources=["tool"],
+            order_by_last_active=True,
+        )
+
     def test_current_child_session_excludes_root_lineage_even_when_child_id_is_longer(self):
         from unittest.mock import MagicMock