ci: use Blacksmith runners in CI and integration workflows

[benvinegar]

Summary

• switch CI workflow jobs from ubuntu-latest to the Blacksmith runner class used in modem
• switch integration workflow jobs to the same runner class
• use a per-workflow YAML anchor (&default-runner) to avoid repeating the runner label

Testing

• workflow-only change (no local runtime tests)

[greptile-apps]

Greptile Summary

Migrated CI and integration workflows from ubuntu-latest to Blacksmith runners (blacksmith-4vcpu-ubuntu-2404). The change uses YAML anchors (&default-runner and *default-runner) to avoid repetition across jobs, following the same pattern used in the modem repository.

Confidence Score: 5/5

• Safe to merge - workflow configuration change with no runtime impact
• This is a straightforward infrastructure change that only modifies the GitHub Actions runner platform. The YAML anchor syntax is correct and all jobs properly reference the anchor. No logic changes, no security implications, and no runtime behavior changes.
• No files require special attention

Important Files Changed

Filename	Overview
.github/workflows/ci.yml	Replaced ubuntu-latest with Blacksmith runner using YAML anchor pattern across all jobs
.github/workflows/integration.yml	Replaced ubuntu-latest with Blacksmith runner using YAML anchor pattern across all jobs

_{Last reviewed commit: 8cd27c9}