Fix runner requirements to schedule pathways workload

[SurbhiJainUSC]

Description

Unable to schedule pathways workload with XPK==0.6.0: https://paste.googleplex.com/6583669159493632

This Pr updates runner requirements to install XPK>=1.8.0

Tests

uv pip install -e .[runner] --resolution=lowest
xpk workload create-pathways ....

Checklist

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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