fix: incorrect history when user aborts in-progress toolUse

[jguoamz]

Problem

• incorrect history when user aborts in-progress toolUse, this leads to incorrect history which confuses LLM and takes long time to recover

Solution

• Populating the previous toolResult back when user aborts instead of simply dropping it
• Fix a bug where modelId can be empty string which causes 400

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[tsmithsz]

nit: Could we add a unit test for this case?

[jguoamz]

nit: Could we add a unit test for this case?

normally yes, but since we have a new refactoring soon, will skip to deploy the fix first