2 new efficiency skills to reduce cost and wasted cpu cycles in github actions and codespaces

[mutl3y]

Pull Request Checklist

• I have read and followed the CONTRIBUTING.md guidelines.
• I have read and followed the Guidance for submissions involving paid services.
• My contribution adds a new instruction, prompt, agent, skill, or workflow file in the correct directory.
• The file follows the required naming convention.
• The content is clearly structured and follows the example format.
• I have tested my instructions, prompt, agent, skill, or workflow with GitHub Copilot.
• I have run npm start and verified that README.md is up to date.
• I am targeting the staged branch for this pull request.

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Description

Adds 2 new skills,

• github-actions-efficiency skill focused on reducing GitHub Actions waste.
• github-codespaces-efficiency skill focused on reducing GitHub Codespaces waste.

These skills provide:

• A lean SKILL.md entry point with scope, workflow, output shape, and review rubric.
• Focused references for Actions audits, Codespaces optimization, reporting, and concrete patterns.
• Updated generated skills documentation via npm run build.

Validation run locally:

• node ./eng/validate-skills.mjs
• npm run build

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Type of Contribution

• New skill file.
• Update to existing instruction, prompt, agent, plugin, skill, or workflow.

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Additional Notes

This PR targets staged and is opened from the contributor fork branch mutl3y:workflow_cost.

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By submitting this pull request, I confirm that my contribution abides by the Code of Conduct and will be licensed under the MIT License.

[github-actions]

🔍 Skill Validator Results

✅ All checks passed

Scope	Checked
Skills	2
Agents	1
Total	3
Severity	Count
---	---:
❌ Errors	0
⚠️ Warnings	0
ℹ️ Advisories	0

Summary

Level	Finding
ℹ️	Found 2 skill(s)
ℹ️	[github-actions-efficiency] 📊 github-actions-efficiency: 866 BPE tokens [chars/4: 1,051] (detailed ✓), 10 sections, 1 code blocks
ℹ️	[github-codespaces-efficiency] 📊 github-codespaces-efficiency: 734 BPE tokens [chars/4: 904] (detailed ✓), 10 sections, 1 code blocks
ℹ️	✅ All checks passed (2 skill(s))

Full validator output

```text Found 2 skill(s) [github-actions-efficiency] 📊 github-actions-efficiency: 866 BPE tokens [chars/4: 1,051] (detailed ✓), 10 sections, 1 code blocks [github-codespaces-efficiency] 📊 github-codespaces-efficiency: 734 BPE tokens [chars/4: 904] (detailed ✓), 10 sections, 1 code blocks ✅ All checks passed (2 skill(s)) ```

[Copilot]

Pull request overview

Adds two new agent skills aimed at reducing GitHub Actions and GitHub Codespaces spend by guiding Copilot through opinionated audits, fix prioritization, and reporting. The skills follow the existing skills/ layout (SKILL.md plus references/ material) and are registered in the generated skills index.

Changes:

• New github-actions-efficiency skill with SKILL.md and four references (actions, patterns, reporting, review-rubric).
• New github-codespaces-efficiency skill with SKILL.md and two references (codespaces, review-rubric).
• Generated update to docs/README.skills.md listing both new skills.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
skills/github-actions-efficiency/SKILL.md	Entry point describing when/how to apply the Actions efficiency workflow.
skills/github-actions-efficiency/references/actions.md	Detailed Actions audit, gating, matrix and live-validation guidance.
skills/github-actions-efficiency/references/patterns.md	Canonical YAML snippets for caching, concurrency, paths, matrices.
skills/github-actions-efficiency/references/reporting.md	Rules for before/after reporting and follow-up review pass.
skills/github-actions-efficiency/references/review-rubric.md	Rubric for reviewing completed Actions efficiency work.
skills/github-codespaces-efficiency/SKILL.md	Entry point describing the Codespaces efficiency workflow.
skills/github-codespaces-efficiency/references/codespaces.md	Devcontainer/machine/prebuild audit and reporting guidance.
skills/github-codespaces-efficiency/references/review-rubric.md	Rubric for reviewing completed Codespaces efficiency work.
docs/README.skills.md	Adds index entries for both new skills.

[aaronpowell]

Some questions/comments on the skills and a small nit

[aaronpowell]

I don't think this is needed. There's nothing in the description that would encourage the agent to use this skill if it's for a codespace, so this just adds tokens to the context that aren't meaningful.

[aaronpowell]

What about a note in here about ensuring a devcontainer-lock.json file? This is something only relatively recently added so a lot of repos won't have it

[aaronpowell]

The skill is only focusing on analysing existing usages of devcontainers/codespaces, would it be worthwhile adding a little to this still to help onboard those?