There's actually an interesting way to do it with a logic_collision_pair, ai_goal_actbusy, your physics item chair and table, and an info_node_hint.
For this example, name the table "table" and the chair "chair". The NPC will be named "billy".
For logic_collision_pair 1, attachment 1 is "table" and 2 is "billy". Start with Collisions Disabled, "Yes".
For logic_collision_pair 2, attachment 1 is "chair" and 2 is "billy". Start with Collisions Disabled, "Yes".
The info_node_hint should be of the World: Act Busy type and the sequence to play in the "Hint Activity" box.
The ai_goal_actbusy should affect "billy" (Search by entity name, not classname).
All you need to do now, is use a trigger or logic_auto to give an OnTrigger or OnMapSpawn with a ForceNPCtoActBusy input.
You're done!