Replace custom Slack file upload with official slack-github-action

[Copilot]

Replaces custom curl-based Slack API calls with the official slackapi/slack-github-action@v2.1.1 for uploading WCAG reports.

Changes

• Before: 48 lines of bash with manual API orchestration (files.getUploadURLExternal, upload, files.completeUploadExternal)
• After: Single action step using files.uploadV2 method

- name: Upload WCAG report to Slack
  if: always()
  uses: slackapi/slack-github-action@v2.1.1
  with:
    method: files.uploadV2
    token: ${{ secrets.SLACK_BOT_TOKEN }}
    payload: |
      channel_id: ${{ secrets.SLACK_CHANNEL_ID }}
      initial_comment: "WCAG rapport:"
      file: "./wcag-report.txt"
      filename: "wcag-report.txt"

Preserves existing behavior: weekly Sunday runs at 02:00 UTC, manual trigger capability, uploads on both success and failure.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• docs.slack.dev
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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