feat(mcp): add preset setup and capability mentions

tests/agent/test_session_manager_history.py

@@ -56,6 +56,20 @@ def test_list_sessions_includes_user_preview(tmp_path):
     assert rows[0]["preview"] == "帮我总结一下 OpenAI 的最新硬件计划"
 
 
+def test_list_sessions_bounds_preview_scan(tmp_path):
+    manager = SessionManager(tmp_path)
+    session = manager.get_or_create("websocket:chat-long-preview")
+    for index in range(220):
+        session.add_message("assistant", f"assistant trace {index}")
+    session.add_message("user", "this should not force a full sidebar scan")
+    manager.save(session)
+
+    rows = manager.list_sessions()
+
+    assert rows[0]["key"] == "websocket:chat-long-preview"
+    assert rows[0]["preview"] == "assistant trace 0"
+
+
 # --- Original regression test (from PR 2075) ---
 
 def test_get_history_drops_orphan_tool_results_when_window_cuts_tool_calls():