[26.0] Fix storing origin for workflow landing requests

[mvdbeek]

The origin field was being accepted in the payload but not stored to the model in create_workflow_landing_request(). This was inconsistent with create_tool_landing_request() which correctly stores the origin. Added a test to verify the origin is preserved through create and claim operations.

https://claude.ai/code/session_01Nk9FaZ1BsPghEvrdJbNQJQ

How to test the changes?

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• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
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  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

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