Only spin up agents and viewport when needed

[mmurad2]

Motivation
It currently takes several seconds for a plan to be generated with most of the latency attributed to the websurfer container spinning up. Additionally, with the addition of MCP agents, not all user queries will require the websurfer agent being available.

Proposed solution

• Implement lazy initialization of all agents (not just Websurfer)
• Have the browser viewpoint closed by default and only open it for the step(s) of the plan where WebSurfer is required

[mmurad2]

Update: use lazy_init method for all agents (not just WebSurfer) -- only call the agents when a message is received

[mmurad2]

To do: benchmark time to generate plan with/without lazy init