JS/TS Agent Protocol v0.2.0

[jakubno]

Is your feature request related to a problem? Please describe.
The agent protocol spec has been updated, we need to update JS SDK to match the spec.

Describe the solution you'd like
Python SDK has been refactored quite a lot, you should imitate the python implementation .

• We added artifacts
• Each task has own workspace where it can save the files (this should be configurable with environment variable AGENT_WORKSPACE)
• There' s download endpoint
• We added db property to Agent class. Without changes it default to in memory storage, but the user should be able to change it to his preferred storage (probably some form of database).
• The task / step handler logic has been reworked. Now the functions receive Task / Step on the input. This allows agent to run statelessly
• Routes should be extensible, if the agent want to add another endpoint or change the default implementation, he should be able to.

[hackgoofer]

#68