Build for arm64 as well as amd64

[michaelherold]

When you want to use Understory on a Mac, you'd prefer to have the container run in the default architecture rather than the translation layer.

This change makes sure that the build system builds the container for both ARM and x86 architectures.

Summary by CodeRabbit

• New Features
  • Docker images are now published for both AMD64 and ARM64 platforms, improving compatibility across hardware architectures.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: b8aa0b94-4952-468e-9c39-ea3a080855eb

📥 Commits

Reviewing files that changed from the base of the PR and between 0b20d7b and 6bd85f6.

📒 Files selected for processing (1)

• .github/workflows/docker.yml

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📝 Walkthrough

Walkthrough

The Docker publish workflow now enables ARM64 emulation and builds images for both linux/amd64 and linux/arm64.

Changes

Docker image publishing

Layer / File(s)	Summary
Configure multi-platform Docker builds .github/workflows/docker.yml	The publish job adds QEMU support for ARM64 emulation and configures Docker Buildx to publish linux/amd64 and linux/arm64 images.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Merge Risk: ⚪ Minimal · up to 6bd85

This change extends container publishing to ARM64 alongside AMD64 for better native support on Apple Silicon. No actionable merge-blocking risk remains beyond normal checks and review.

Suggested reviewers: thecodacus

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: building container images for both ARM64 and AMD64.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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