#29051 ci(repo variables): literal fallback for the check job's pool runs-on (fixes CI fast guards on main)

CI fast guards is red on main from 9197d7fe (#28864) on. The failing step is Validate repository variable defaults (tests/test_ci_repo_variable_defaults.py):

ci-repo-variables.yml:48: runs-on reads vars.RUNNER_POOLS with no literal runner label to fall back to; a fork pull request gets an empty runs-on

#28864 moved the Check repository variables job onto fromJSON(vars.RUNNER_POOLS).linux with nothing after it. This adds || 'blacksmith-32vcpu-ubuntu-2404' (the linux pool's first member). The job still reads the pool first, so it still never waits on LINUX_RUNNER.

Verified: the 41 guard steps that cover workflows, runners, variables and pools pass on this head (the variable-defaults step failed before the change).

Risk: low. One runs-on expression; the job only runs on manaflow-ai/cmux.

🤖 Generated with Claude Code

Agent session: agent session

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Summary by cubic

Fixes CI fast guards on main by giving the "Check repository variables" job's runs-on a literal fallback. After #28864 moved the job onto fromJSON(vars.RUNNER_POOLS).linux, a fork pull request gets an empty runs-on, failing the "Validate repository variable defaults" guard step.

The fallback is 'blacksmith-32vcpu-ubuntu-2404', the linux pool's first member. The job still reads the pool first, so it still never waits on LINUX_RUNNER.

Summary by CodeRabbit

• Chores
  • Updated CI runner selection so repositories under manaflow-ai use the blacksmith-32vcpu-ubuntu-2404 runner when no Linux runner pool is configured. Other repositories continue to use ubuntu-24.04.