[Bug]: maturity, etc. are not supported frontmatter for agents in copilot CLI

[plasne]

Component

Custom Agents

Bug Description

None of the custom agents could be used in Copilot CLI (prerelease v0.0.400-0) because it doesn't like the extra frontmatter.

I will also open an issue with the copilot CLI team because VSCODE apparently ignores extra frontmatter which seems more useful.

True or not, this is what Copilot had to say: "This is a case where Copilot CLI is stricter than VS Code. The maturity field isn't part of the official agent schema - both environments technically don't support it, but VS Code silently ignores unknown fields while Copilot CLI warns about them."

And to be clear, it does more than just warn. It won't let you use the agent.

Copilot encountered the following issues:
• /Users/plasne/Documents/experiment-catalog/.github/agents/ado-prd-to-wit.agent.md: agent uses unsupported
fields: maturity
• /Users/plasne/Documents/experiment-catalog/.github/agents/adr-creation.agent.md: agent uses unsupported
fields: maturity
• /Users/plasne/Documents/experiment-catalog/.github/agents/arch-diagram-builder.agent.md: agent uses
unsupported fields: maturity
• /Users/plasne/Documents/experiment-catalog/.github/agents/brd-builder.agent.md: agent uses unsupported
fields: maturity
• /Users/plasne/Documents/experiment-catalog/.github/agents/doc-ops.agent.md: agent uses unsupported fields:
maturity
• /Users/plasne/Documents/experiment-catalog/.github/agents/gen-data-spec.agent.md: agent uses unsupported
fields: maturity
• /Users/plasne/Documents/experiment-catalog/.github/agents/gen-jupyter-notebook.agent.md: agent uses
unsupported fields: maturity
• /Users/plasne/Documents/experiment-catalog/.github/agents/gen-streamlit-dashboard.agent.md: agent uses
unsupported fields: maturity
• /Users/plasne/Documents/experiment-catalog/.github/agents/github-issue-manager.agent.md: agent uses
unsupported fields: maturity
• /Users/plasne/Documents/experiment-catalog/.github/agents/hve-core-installer.agent.md: agent uses unsupported
fields: maturity
• /Users/plasne/Documents/experiment-catalog/.github/agents/memory.agent.md: agent uses unsupported fields:
maturity, handoffs
• /Users/plasne/Documents/experiment-catalog/.github/agents/pr-review.agent.md: agent uses unsupported fields:
maturity
• /Users/plasne/Documents/experiment-catalog/.github/agents/prd-builder.agent.md: agent uses unsupported
fields: maturity
• /Users/plasne/Documents/experiment-catalog/.github/agents/prompt-builder.agent.md: agent uses unsupported
fields: maturity, handoffs
• /Users/plasne/Documents/experiment-catalog/.github/agents/rpi-agent.agent.md: agent uses unsupported fields:
maturity, argument-hint, handoffs
• /Users/plasne/Documents/experiment-catalog/.github/agents/security-plan-creator.agent.md: agent uses
unsupported fields: maturity
• /Users/plasne/Documents/experiment-catalog/.github/agents/task-implementor.agent.md: agent uses unsupported
fields: maturity, handoffs
• /Users/plasne/Documents/experiment-catalog/.github/agents/task-planner.agent.md: agent uses unsupported
fields: maturity, handoffs
• /Users/plasne/Documents/experiment-catalog/.github/agents/task-researcher.agent.md: agent uses unsupported
fields: maturity, handoffs
• /Users/plasne/Documents/experiment-catalog/.github/agents/task-reviewer.agent.md: agent uses unsupported
fields: maturity, handoffs
• /Users/plasne/Documents/experiment-catalog/.github/agents/test-streamlit-dashboard.agent.md: agent uses
unsupported fields: maturity

Expected Behavior

To be able to use the agents in Copilot CLI

Steps to Reproduce

I used symlinks to bring the extension folders into scope for the Copilot CLI.

Additional Context

I am a Microsoft employee and can be reached as pelasne on Teams.

[plasne]

There is an issue for this on copilot CLI repo: github/copilot-cli#1195