Drop Ubuntu 20.04 support

[yorch]

Summary

• Remove Ubuntu 20.04 from supported versions (EOL April 2025)
• Minimum supported version is now Ubuntu 22.04
• Updated bootstrap.sh, run-tests.sh, CI matrix, and AGENTS.md

Test plan

• CI passes for ubuntu:22.04 and ubuntu:24.04

🤖 Generated with Claude Code

Summary by CodeRabbit

• Chores

  • Updated CI pipeline to test on Ubuntu 22.04 and 24.04 only; removed Ubuntu 20.04 from test matrix

• Documentation

  • Updated project documentation to reflect supported Ubuntu versions (22.04 and 24.04)

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[coderabbitai]

Caution

Review failed

The pull request is closed.

📝 Walkthrough

Walkthrough

The pull request removes Ubuntu 20.04 from all supported versions across CI workflows, test infrastructure, configuration scripts, and documentation. Ubuntu 22.04 and 24.04 become the only supported LTS versions.

Changes

Cohort / File(s)	Summary
CI and Test Infrastructure .github/workflows/ci.yaml, run-tests.sh	Removed ubuntu:20.04 from the CI matrix and base image array; testing now runs only on Ubuntu 22.04 and 24.04.
Version Configuration bootstrap.sh	Removed "20.04" from the UBUNTU_SUPPORTED_VERSIONS array, leaving only 22.04 and 24.04.
Documentation AGENTS.md	Updated project overview, supported versions list, and test invocation examples to reflect removal of Ubuntu 20.04; adjusted CI matrix commentary from three to two versions.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 Off hops Ubuntu twenty, time to say goodbye,
With twenty-two and twenty-four, we reach for the sky,
These old versions fade away, our support runs lean,
Cleaner config, faster tests—the freshest we've seen! 🌱

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch remove-ubuntu-2004-support

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[Copilot]

Pull request overview

This pull request removes support for Ubuntu 20.04, which is approaching end-of-life in April 2025. The minimum supported Ubuntu version is now 22.04.

Changes:

• Removed Ubuntu 20.04 from test infrastructure and CI matrix
• Updated supported versions array in bootstrap script
• Updated documentation to reflect Ubuntu 22.04 as the minimum version

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
run-tests.sh	Removed "ubuntu:20.04" from BASE_IMAGES array used for testing
bootstrap.sh	Removed "20.04" from UBUNTU_SUPPORTED_VERSIONS validation array
AGENTS.md	Updated project overview to reflect Ubuntu 22+ minimum, removed 20.04 from supported versions list, and updated CI matrix description from "three versions" to "both versions"
.github/workflows/ci.yaml	Removed "ubuntu:20.04" from the CI matrix strategy

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