chore: consolidate release and publish into single multi-job workflow

[Copilot]

Releases created by release-please-action via GITHUB_TOKEN don't reliably trigger downstream on: release workflows, causing the publish step to never run automatically.

Changes

• .github/workflows/release.yml — rewritten as a two-job pipeline:

  • release-please job: runs on push to main, exposes manifest path-scoped outputs
  • publish job: gated once via needs/if on release_created == 'true'; runs checkout → build → test → pack → NuGet publish → GitHub release upload → PR label

  jobs:
    release-please:
      outputs:
        release_created: ${{ steps.release.outputs['Dataverse.Extensions.DependencyInjection--release_created'] }}
        tag_name: ${{ steps.release.outputs['Dataverse.Extensions.DependencyInjection--tag_name'] }}
      ...
    publish:
      needs: release-please
      if: needs.release-please.outputs.release_created == 'true'
      ...

• .github/workflows/publish.yml — deleted; replaced by the publish job above

• workflow_dispatch removed; no manual trigger needed in the new design

• Permissions are job-scoped rather than workflow-level