Add onboarding welcome action for [ONBOARD] issues

[yunjchoi]

Adds a GitHub Action that welcomes new contributors when an Azure MCP onboarding issue is filed.

Trigger: issues (opened, labeled), gated on both the onboarding and Azure.Mcp.Server labels applied by the Azure MCP - Service Onboarding Request template. Requiring both labels scopes this to Azure MCP only — the generic New Microsoft MCP Server Onboarding Request template also uses onboarding but pairs it with Template.Mcp.Server, so it will not trigger this action.

Behavior: Posts a comment pointing contributors to the CONTRIBUTING.md guide and encouraging them to try the @onboarding Copilot agent. A hidden marker prevents duplicate comments across the multiple label events.

Permissions: issues: write only.

[Copilot]

Pull request overview

Adds a GitHub Actions workflow that automatically welcomes new contributors when an Azure MCP onboarding issue is created (or later labeled), posting a single guidance comment with links to contributing docs and the @onboarding Copilot agent.

Changes:

• Add an issues-triggered workflow (opened, labeled) gated on both onboarding and Azure.Mcp.Server labels.
• Post a welcome comment via actions/github-script, with an HTML marker to prevent duplicate comments across multiple label events.

Invoking Livetests

Copilot submitted PRs are not trustworthy by default. Users with write access to the repo need to validate the contents of this PR before leaving a comment with the text /azp run mcp - pullrequest - live. This will trigger the necessary livetest workflows to complete required validation.

[jongio]

One version consistency note flagged inline.

[jongio]

Incremental review of the v7 to v8 fix. The repo's other workflows pin actions/github-script by SHA at v9. One inline suggestion below.

[jongio]

Logic, permissions, and duplicate-prevention all look correct. The label gating (onboarding + Azure.Mcp.Server) properly scopes to Azure MCP onboarding only, and the hidden marker prevents re-posting.

The SHA-pinning concern is already covered by existing feedback. One minor suggestion below about redundant workflow runs.

[jongio]

One blocking issue from the latest push. The rest of the changes (SHA-pinning github-script and adding concurrency to dedupe the multiple labeled events) look right.

• .github/workflows/onboarding-welcome.yml: the jobs: block lost its welcome: job id and has a duplicated runs-on, so it no longer parses as a valid job. Details inline.

[jongio]

Incremental review of the latest push. The welcome: job id is restored, which fixes half of what I flagged, but the duplicate runs-on is still present so the workflow still won't parse. One inline note.

[jongio]

Confirmed the latest commit drops the duplicate runs-on, so .github/workflows/onboarding-welcome.yml now parses as a single valid welcome job (checked with a YAML parse). The concurrency dedupe on the issue number and the SHA-pinned github-script@3a2844b... (v9) are both in place, and the label gate still requires both onboarding and Azure.Mcp.Server. Nothing outstanding from me on this workflow.