fix: ensure exit cause is propagated and sent to worker

[nabil-Tounarti]

No description provided.

[Copilot]

Pull Request Overview

This PR fixes a bug where the exit cause from pre-compute app failures was not being properly propagated to the worker API. The fix ensures that the actual exit cause returned by the pre-compute app is captured and sent to the worker, rather than always using a default "unknown issue" cause.

• Refactored exit cause handling to capture the actual error from pre_compute_app.run()
• Updated test to use a specific exit cause instead of the default unknown issue
• Enhanced test verification with proper mock expectations

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