fix: use GitHub Copilot CLI for AI PR summaries instead of GitHub Models API

[Copilot]

The AI PR summary step was calling the GitHub Models API directly, which responded with 400 and silently skipped the summary. Replaced with GitHub Copilot CLI (@github/copilot) per the official Actions integration docs.

Changes

• New reusable workflow .github/workflows/ai-pr-summary.yml (workflow_call)
  • Installs @github/copilot CLI (Node 20)
  • Authenticates via COPILOT_GITHUB_TOKEN (PAT with "Copilot Requests" permission, passed as COPILOT_TOKEN secret)
  • Fetches PR diff → asks Copilot CLI to summarize → posts result as a PR comment
  • Fails fast with a clear error if the diff is empty or summary.md is not produced

Usage from monorepo (or any repo)

jobs:
  summarize:
    uses: webmonitoring/.github/.github/workflows/ai-pr-summary.yml@develop
    with:
      pr_number: ${{ github.event.pull_request.number }}
    secrets:
      COPILOT_TOKEN: ${{ secrets.COPILOT_TOKEN }}

Prerequisite: Create a fine-grained PAT with the Copilot Requests permission and store it as the COPILOT_TOKEN Actions secret in the calling repository.

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.