Automate custom agent assignment in weekly maintenance workflow

[Copilot]

The Weekly Maintenance workflow creates issues but doesn't automatically assign the project-maintainer custom agent, requiring manual intervention.

Changes

• GraphQL agent lookup: Query repository.customAgent(slug: "project-maintainer") to retrieve agent ID
• Agent assignment: Use assignCopilotAgentToAssignable mutation to bind agent to created issue
• Error handling: Fallback to comment-based mentions if GraphQL operations fail
• Permissions: Added id-token: write for agent assignment API access

Implementation

// Query for agent ID
const agentResponse = await github.graphql(agentQuery, {
  owner: context.repo.owner,
  repo: context.repo.repo,
  slug: 'project-maintainer'
});

// Assign agent to issue
await github.graphql(assignMutation, {
  assignableId: issue.data.node_id,
  customAgentId: agentResponse.repository.customAgent.id
});

The workflow now automatically assigns the agent on issue creation, enabling true hands-off weekly maintenance.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[Feature]: Weekly maintenance task is not automatically starting</issue_title>
<issue_description>### Problem Statement

The Weekly Maintenance tries to kick off the 'project-maintainer' custom GitHub agent to keep the project up to date every week; however the 'project-maintainer' custom GitHub agent does not run.

Proposed Solution

It seems like the correct way to kick off a copilot agent is to extend the actions/github-script step to:

1. Query the customAgentId for the 'project-maintainer' custom GitHub agent
2. Create the issue and save the issue ID (already done)
3. Use the GraphQL API to perform the assignCopilotAgentToAssignable mutation to assign the issue to the customAgentId

Alternatives Considered

No response

Usage Examples

Benefits

This would allow for periodic automatic maintenance of the project.

Priority

Medium - Would improve my workflow

Willingness to Contribute

Yes, I can submit a pull request

Additional Context

No response

Checklist

• I have searched existing issues to ensure this is not a duplicate
• I have provided a clear description of the feature
• I have explained why this feature would be useful</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Feature]: Weekly maintenance task is not automatically starting #48

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