Split preview link generation out of status-checker into a dedicated action

[Copilot]

status-checker was handling two separate concerns: OPS status evaluation and PR preview-link generation. This change separates preview-link generation into its own action while narrowing status-checker to status-only behavior.

• New action surface

  • Adds actions/preview-link-generator as the dedicated action for building and updating PR preview links.
  • Keeps preview-specific inputs (docs_path, url_base_path, collapsible_after, max_row_count, opaque_leading_url_segments) with the preview action instead of status-checker.

• Status-checker scope reduction

  • Removes preview table generation from actions/status-checker/src/main.ts.
  • Removes the obsolete mode-based branching and associated input/type plumbing so status-checker now only evaluates OpenPublishing build status.

• Packaging/layout

  • Adds a separate preview entrypoint and packages it into the new action’s own dist/ output.
  • Updates action metadata and docs to reflect the split.

• Workflow coverage

  • Extends Node action validation triggers to include changes under actions/preview-link-generator/**.

Example usage of the new action:

on: [pull_request_target]

jobs:
  preview_link_generator_job:
    runs-on: ubuntu-latest
    steps:
    - uses: dotnet/docs-tools/actions/preview-link-generator@main
      with:
        repo_token: ${{ secrets.GITHUB_TOKEN }}

[Copilot]

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[BillWagner]

This LGTM. Let's