Enable AI Agentic Workflow for Buildkite build failure analysis

[Copilot]

Enable automatic AI-powered analysis of Buildkite build failures on pull requests by implementing the same workflow infrastructure available in elastic-agent.

Changes

Workflow Configuration: Added .github/workflows/trigger-pr-buildkite-detective.yml that:

• Triggers on Buildkite status failures
• Delegates analysis to Elastic AI GitHub Actions infrastructure (gh-aw-estc-pr-buildkite-detective.lock.yml@v0)
• Includes instructions to cross-reference known flaky test issues
• Requires COPILOT_GITHUB_TOKEN and BUILDKITE_LOGS_API_TOKEN repository secrets

name: PR Buildkite Detective
on:
  status:

permissions:
  actions: read
  contents: read
  issues: write
  pull-requests: write

jobs:
  run:
    if: >-
      github.event.state == 'failure' &&
      contains(github.event.context, 'buildkite')
    uses: elastic/ai-github-actions/.github/workflows/gh-aw-estc-pr-buildkite-detective.lock.yml@v0
    secrets:
      COPILOT_GITHUB_TOKEN: ${{ secrets.COPILOT_GITHUB_TOKEN }}
      BUILDKITE_API_TOKEN: ${{ secrets.BUILDKITE_LOGS_API_TOKEN }}

[mergify]

This pull request does not have a backport label. Could you fix it @Copilot? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.
• If no backport is necessary, please add the backport-skip label