CP-3237: migrate github actions to warpbuild runners

[JeffTax]

Summary

• Replace runs-on: ubuntu-latest with WarpBuild runs-on: warp-ubuntu-latest-x64-2x in GitHub Actions workflows.
• Aligns this repo with the rest of the kintsugi-tax org (platform and most service repos already on WarpBuild).

Jira

CP-3237

Tests

CI on this PR should confirm jobs run on WarpBuild runners.

Document Checklist

• N/A — runner label change only

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Note

Low Risk
Runner label-only change with no application or workflow logic changes; main risk is CI failing if WarpBuild labels or org integration are misconfigured.

Overview
Switches all CI jobs in .github/workflows/ci.yml from GitHub-hosted ubuntu-latest to WarpBuild warp-ubuntu-latest-x64-2x runners.

lint-and-test, auto-tag, and release keep the same steps, timeouts, and conditions; only the runs-on label changes so this repo matches the org’s WarpBuild setup.

^{Reviewed by Cursor Bugbot for commit 0400e34. Bugbot is set up for automated code reviews on this repo. Configure here.}

[JeffTax]

CI note: lint-and-test stays queued with no WarpBuild runner (previous run sat queued ~75m before cancel). Org WarpBuild app is installed; other CP-3237 repos got runners successfully.

Likely needs WarpBuild-side enabling for this repo’s workflows before merge.

[JeffTax]

Closing — squawk-pre-commit is open source; leaving GitHub-hosted runners as-is. Not applying the WarpBuild migration here.