fix execute_task to prevent results ghosting

[shikha130vv]

Fix task execution result handling when .get attribute or content key is missing

Description

Previously, the code assumed that the task result always had a .get method or a content key, which caused empty or missing outputs when the result object was a plain string or a non-dict type.
This update adds safer handling for different result formats — including plain strings, objects without .get(), and dict-like or strands-style objects — to ensure the output is always correctly normalized into text and metrics.

Related Issues

Documentation PR

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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[shikha130vv]

@mkmeral could you help merge this PR?