Support DBOS Agent by wrapping run as DBOS workflows and moving model requests and MCP to DBOS steps

[qianl15]

Summary

Closes #2629

This PR integrates DBOS with Agent.run and related methods to provide out-of-the-box durable execution and checkpointing.

Changes

• Workflows:

  • Agent.run and Agent.run_sync are now decorated as DBOS workflows.
  • Users no longer need to manually wrap these functions in DBOS workflows.

• Steps:

  • Model requests and MCP calls (get_tools, call_tool) are decorated as DBOS steps.
  • Outside DBOS, these remain ordinary functions.
  • Inside DBOS workflows, outputs are automatically checkpointed in Postgres.

• Tooling:

  • Users may pass in DBOS-decorated functions (workflows, steps, transactions) as tools.
  • The integration does not automatically wrap tools in DBOS decorators, so users retain full control. For example, they can pass in a workflow which will be invoked as a child workflow; or they can pass in a step.
  • Tools behave as normal functions when not used with DBOS.

TODO

• Add documentation
• Update to V1 API.
• Make human-in-the-loop work with DBOSAgent.

[qianl15]

All review comments addressed. Updates from last review:

• Switched to use SQLite instead of Postgres for CI tests.
• Made DBOS an optional dependency for pydantic-ai.
• Added a full draft of the dbos.md docs.

[DouweM]

@qianl15 Thanks Qian, we're getting there :) If you could port the HITL tool approval test we have for Temporal, as you suggested in the description, that'd be great!

[DouweM]

Are they sent to Logfire automatically, assuming it is set up?

It would be great to see that in the span tree in the test_complex_agent_run_in_workflow test -- as you can see in the temporal test it has StartWorkflow events

[qianl15]

Updated the docs and tests for this. Right now DBOS and Logfire generate overlapping spans since OpenTelemetry doesn't interoperate cleanly, so I changed the defaults/docs to disable DBOS OTLP traces.

Because DBOS runs workflows and steps as normal function calls, you won't see extra spans like "StartWorkflow" or "RunWorkflow" events.

[qianl15]

@qianl15 Thanks Qian, we're getting there :) If you could port the HITL tool approval test we have for Temporal, as you suggested in the description, that'd be great!

Thanks @DouweM for the review! I addressed all your comments and added the HITL tests (both async and sync work as expected).