Pathfinder command

[mitzimorris]

Summary:

Expose the Pathfinder service (stan-dev/stan#3123) in CmdStan

Description:

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Reproducible Steps:

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Current Output:

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Expected Output:

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Additional Information:

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Current Version:

v2.31.0

[mitzimorris]

WIP started last year: https://github.com/stan-dev/cmdstan/tree/feature/multi-pathfinder