feat: combined multi-architecture support (amd64 + arm64)

[anchapin]

Summary

Combined implementation of multi-architecture Docker support (linux/amd64 + linux/arm64), consolidating the beneficial aspects of PR #213 (rh0dium, feature/multi-arch-support) and PR #217 (anchapin, arm-image) into a single, verified PR targeting develop.

Why combine

Both PRs address the same feature (multi-arch images, originally requested in #85) and were built against identical baselines, but use conflicting deployment strategies:

	PR #213	PR #217
Strategy	Single docker buildx build --push --platform=linux/amd64,linux/arm64	Native per-arch matrix (ubuntu-24.04 + ubuntu-24.04-arm) → push arch-suffixed images → buildx imagetools create
arm64 source	S3 (...-arm64.deb)	GitHub release assets

Verified finding: the S3 bucket openstudio-ci-builds does not publish arm64 builds (...-arm64.deb returns HTTP 404), so PR #213's arm64 builds cannot succeed. PR #217's GitHub-release approach works — NatLabRockies/OpenStudio is the canonical repo (NREL redirects to it) and publishes both arches for stable releases. Additionally, PR #213's QEMU-emulation approach is impractical here: the image compiles Ruby 3.2.2 from source and downloads a ~1 GB .deb (emulation would take hours).

What this PR does

Adopts PR #217's native matrix architecture and folds in the useful pieces of PR #213:

• Dockerfile: TARGETARCH selects the correct .deb — S3 for amd64 (-x86_64), GitHub release assets for arm64 (with 10-char SHA).
• Workflow (docker-openstudio.yml):
  • setup job resolves per-arch download URLs (GitHub releases for stable versions, S3 for pre-releases).
  • docker job runs a native matrix (amd64 on ubuntu-24.04, arm64 on ubuntu-24.04-arm), builds, tests, and pushes *-amd64/*-arm64 images. Radiance rtrace test is skipped on arm64 (packaged binary not executable there).
  • docker-manifest job merges arch images into canonical tags via docker buildx imagetools create, with explicit docker/setup-buildx-action@v3 (from PR Add multi-architecture support (amd64 + arm64) #213).
  • Pre-flight curl check fails fast with a clear message when an artifact is unavailable (e.g. arm64 pre-releases only publish x86_64).
• get_image_tags.sh: shared tag logic consumed by both deploy_docker.sh and merge_manifests.sh (DRY, no drift).
• deploy_docker.sh: rewritten to push arch-suffixed images (canonical tags assembled later by the manifest job so parallel arch pushes never clobber).
• merge_manifests.sh: new — merges arch-suffixed images into canonical multi-arch manifests.

Deliberate changes vs the source PRs

• Default OpenStudio bumped to 3.11.0 final (241b8abb4d) instead of PR Add multi-architecture support for OpenStudio Docker images #217's revert to 3.10.0 and instead of the current rc1 default. 3.11.0 final is the first version with both amd64 and arm64 Ubuntu-24.04 assets on GitHub releases (verified: both URLs return 200). The rc1 only exists on S3 as x86_64.
• Fixed latent bugs in PR Add multi-architecture support for OpenStudio Docker images #217: removed dead inputs.docker_manual_image_tag env references (no such input exists in this workflow) and made get_image_tags.sh robust to an unset DOCKER_MANUAL_IMAGE_TAG under set -u.
• PR Add multi-architecture support (amd64 + arm64) #213's manual_installer_test.yml Ubuntu-24.04 + tag-description updates were already merged into the baseline via PRs feat: add workflow_dispatch for on-demand .sif builds and update to ubuntu-24.04 #214/feat: merge workflow_dispatch trigger to develop branch #215 — no change needed.

Testing

• All shell scripts pass bash -n and shellcheck.
• Tag resolution logic verified for: master/develop branches, manual version tags (3.11.0-rc3), manual dev tags, and PR events (skip, exit 0).
• Stable URL resolution for 3.11.0 final verified live (both amd64 and arm64 assets return HTTP 200).
• Pre-release edge case verified: amd64 URL resolves, arm64 pre-flight fails with a clear message.

Note: the arm64 CI leg uses the GitHub-hosted ARM runner (ubuntu-24.04-arm). The apptainer job now waits on docker-manifest so it pulls the canonical multi-arch tag.