The --agent flag should put just the Agent Name only

[doggy8088]

Describe the feature or problem you'd like to solve

I wish Copilot CLI can simplify the agent usage

Proposed solution

I have a agent here: .github/agents/Plan.agent.md.

When I want to assign this agent in prompt mode. I have to do this:

copilot --agent Plan.agent -p 'I hope that all the listing pages in the backend can automatically submit queries when search conditions change.'

I wish it can change to:

sh
copilot --agent Plan -p 'I hope that all the listing pages in the backend can automatically submit queries when search conditions change.'

Right now, the error will shown:

No such agent: Plan, available: CSharpExpert.agent, Plan.agent, architect.agent, sql-master-ro.agent, sql-master.agent

Example prompts or workflows

N/A

Additional context

N/A