feat(docker-build-images): enable ARM64 standard runners for private repos

[Copilot]

ARM64 standard runners are now available for private repositories, so the workflow should no longer block ARM64 runner selection in private contexts. The runner pickup strategy is updated to reflect the new availability.

• Runner selection
  • Apply ARM64 standard runner mapping regardless of repo visibility.
• Docs
  • Clarify default runs-on behavior now covers ARM64 standard runners in private repositories.

# ARM64 platform now maps to standard ARM runners in all repos
{ runner: "ubuntu-24.04-arm", platformPattern: /^linux\/arm/ }

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• github.blog
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

On docker-build-images.yml, Regarding this news, https://github.blog/changelog/2026-01-29-arm64-standard-runners-are-now-available-in-private-repositories/

Update runner pick-up strategy

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