Clarify AGENTS.md coding standards

[adrian-rpf]

Summary

• make .rubocop.yml authoritative for machine-checkable Ruby style and remove the duplicated naming rule
• state when focused specs, RuboCop, and the full test suite should run
• make the domain-operation boundary explicit for controllers and mutations
• point CI and runtime-version guidance to .github/workflows/ci.yml and .tool-versions

Tests

• git diff --check
• documentation-only change; runtime tests not run

[Copilot]

Pull request overview

Updates AGENTS.md to better define project-wide standards and expectations for style, behavior, testing, and architectural boundaries, so contributors have clearer guidance when making changes.

Changes:

• Makes the controller/mutation → domain-operation boundary explicit (use lib/concepts/**, add new ops when needed).
• Adds a “Sources of Truth” section to clarify where to look for style, behavior, and project guidance.
• Refines testing guidance to indicate when to run focused specs vs RuboCop vs the full suite.

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[github-actions]

Test coverage

93.43% line coverage reported by SimpleCov.
Run: https://github.com/RaspberryPiFoundation/editor-api/actions/runs/32756493119

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

[github-actions]

This PR is stale because it has been open for 30 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[github-actions]

This PR is stale because it has been open for 30 days with no activity. Remove stale label or comment or this will be closed in 7 days.

[github-actions]

This PR was closed because it has been open for more than 30 days with no activity.