fix(workflow): Allow workflow tasks access results from previous dependent tasks

[foxxqin]

Description

Fix: Workflow tasks cannot get the result from previous dependent tasks.

In https://github.com/strands-agents/tools/blob/main/src/strands_tools/workflow.py
the code:
content = result.get("content", []) if hasattr(result, "get") else getattr(result, "content", [])
is supposed to get the result from previous tasks and save it in the context for later use.

However, the code cannot parse the object of AgentResult type and get the result from the agent run.

I also updated the test cases in tests/test_workflow.py to mock up the ActionResult return value.

Related Issues

#201

Documentation PR

No need to update the documentation, as it's the expected behavior from the workflow tool.

Type of Change

Bug fix

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

• I ran hatch run prepare

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature
• My changes generate no new warnings
• Any dependent changes have been merged and published

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