Verify Markdown Links workflow fails on schedule and workflow_dispatch events #27091

Summary

The Verify Markdown Links workflow (.github/workflows/verify-markdown-links.yml) declares schedule (weekly Sunday cron) and workflow_dispatch triggers, but the underlying get-changed-files composite action only handles pull_request and push events. Every scheduled run fails immediately with:

Unsupported event type: schedule. Supported types: pull_request, push

This has been failing every Sunday since the workflow was introduced in PR #26219 (October 2025).

Steps to Reproduce

1. Go to Actions → Verify Markdown Links → Run workflow
2. Click "Run workflow" on any branch
3. The run fails with: Unsupported event type: workflow_dispatch. Supported types: pull_request, push

Alternatively, wait for the weekly Sunday midnight UTC cron to fire — same error.

Expected Behavior

The workflow should enumerate all markdown files in the repository (since there is no diff to compare for cron/manual runs) and check their links for external link rot.

Actual Behavior

The get-changed-files action calls core.setFailed() because it has no code path for schedule or workflow_dispatch events — only pull_request and push.

Root Cause

.github/actions/infrastructure/get-changed-files/action.yml lines 75-77 — the else branch rejects any event type not in the supported list, and schedule/workflow_dispatch were never added.

Environment

• GitHub Actions, actions/github-script@v7
• Workflow: .github/workflows/verify-markdown-links.yml
• Action: .github/actions/infrastructure/get-changed-files/action.yml