Prevent downstream health GitHub MCP rate-limit failures

[Copilot]

The Internal: Downstream Health workflow could not complete when per-repository GitHub MCP searches triggered the secondary-rate-limit circuit breaker.

• Search strategy: Replace per-repository searches with organization-wide searches, then filter results to discovered downstream repositories.
• Workflow guidance update: Update the downstream health investigation instructions to explicitly require a single org-wide search pass and prohibit per-repo search fan-out to avoid secondary rate limits.
• Compiled workflow: Regenerate the corresponding lock file.

github-search_issues:
  org:elastic commenter:github-actions[bot] updated:>={date}

github-search_pull_requests:
  org:elastic reviewed-by:github-actions[bot] updated:>={date}

• Fixes [aw] Internal: Downstream Health is missing required tool #1878---
  The body of this PR is automatically managed by the Trigger Update PR Body workflow.

[v1v]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved the merge conflict in the generated downstream health lock file while preserving the organization-wide search changes. Merge commit: b602514.