[schema-coverage] feat: Add schema coverage demo for pre-steps field

[github-actions]

Schema Coverage Demo

This PR adds a minimal demo workflow that demonstrates usage of the pre-steps field in the gh-aw frontmatter schema.

Why: The schema feature coverage checker found that pre-steps was not used in any existing workflow.

What: Adds schema-demos/schema-demo-pre-steps.md with a valid, minimal demonstration of this field.

Field Description

Custom workflow steps to run at the very beginning of the agent job, before checkout and any other built-in steps. Use pre-steps to mint short-lived tokens or perform any setup that must happen before the repository is checked out. Step outputs are available via ${{ steps.(id).outputs.(name) }} and can be referenced in checkout.token to avoid masked-value cross-job-boundary issues.

Validation

• Coverage grep confirms schema-demos/schema-demo-pre-steps.md now contains the top-level pre-steps key.
• make build && make fmt could not complete because this runner has Go 1.24.13 locally, while go.mod requires Go 1.25.8, and the toolchain download from proxy.golang.org is blocked by the environment firewall.
• make fmt is blocked by the same missing Go 1.25.8 toolchain.

Warning

Firewall blocked 1 domain

The following domain was blocked by the firewall during workflow execution:

• proxy.golang.org

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "proxy.golang.org"

See Network Configuration for more information.

Generated by 📊 Schema Feature Coverage Checker · ◷

• expires on May 25, 2026, 7:56 AM UTC

[Copilot]

Pull request overview

Adds a minimal schema coverage demo workflow for the pre-steps frontmatter field to bring schema feature coverage to 100%.

Changes:

• New demo workflow file under schema-demos/ following the established sibling-file pattern (matches schema-demo-labels.md and schema-demo-metadata.md).
• Frontmatter exercises the top-level pre-steps key with a single named echo step.

Show a summary per file

File	Description
schema-demos/schema-demo-pre-steps.md	New minimal demo workflow exercising the pre-steps frontmatter field for schema coverage.

Copilot's findings

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• Files reviewed: 1/1 changed files
• Comments generated: 0

[github-actions]

Skills-Based Review 🧠

Applied /grill-with-docs — this PR introduces a new schema demo file, so I checked vocabulary consistency and structural alignment with existing demos.

Key Themes

• Consistent pattern: The new schema-demo-pre-steps.md follows the exact same structure as schema-demo-labels.md and schema-demo-metadata.md.
• Correct vocabulary: The pre-steps field name, description, and inline comments match the project's domain language as defined in the schema and AGENTS.md.
• Minimal and appropriate: The demo uses workflow_dispatch, engine: codex, permissions: contents: read, and a single step — all sensible defaults for a coverage-only workflow.

Positive Highlights

• ✅ Auto-generated PR with a consistent template — easy to review and maintain
• ✅ PR description accurately explains what pre-steps does and why the demo exists
• ✅ The noop safe-output call is correctly included in the task body

Verdict

Approving. The change is purely additive, structurally correct, and aligns with established schema-demo conventions.

🧠 Reviewed using Matt Pocock's skills by Matt Pocock Skills Reviewer · ● 4M