Feature #584 linkcheck_job

[JohnHalleyGotway]

Change Summary

Describe the changes proposed by this pull request:

Closes #584

Runs the link checker as its own Check Links job in the Documentation workflow, concurrently with the docs build. This is the same change made in METplus (dtcenter/METplus#3359, dtcenter/METplus@0db2fb2). Before, Check links was the last step of the Build Documentation job.

• In .github/workflows/documentation.yaml, the new linkcheck job checks out the repository and runs dtcenter/metplus-action-linkcheck@v1 with the same inputs as before. The action sets up Python and installs the docs requirements itself, so the job needs no other steps.
• The docs build result no longer waits for the slower link check, and a broken link now fails Check Links rather than Build Documentation.

Pull Request Testing

• Describe testing already performed for these changes:
  
  Confirmed that the updated workflow file parses as YAML and defines separate documentation and linkcheck jobs. The Documentation workflow run on this PR tests the change itself.

• Recommend testing for the reviewer(s) to perform, including the location of input datasets, and any additional instructions:
  
  Confirm that the Documentation workflow on this PR shows separate Build Documentation and Check Links jobs, and review the Linkcheck Results in the Check Links job summary.

• Do these changes include sufficient documentation updates, ensuring that no errors or warnings exist in the build of the documentation? [Yes] No documentation changes are needed.

• Do these changes include sufficient testing updates? [Yes] No testing changes are needed.

• Will this PR result in changes to the test suite? [No]
  
  If yes, describe the new output and/or changes to the existing output:
  

• Do these changes introduce new SonarQube findings? [No]
  
  If yes, please describe:
  

• Please complete this pull request review by [Fill in date].
  

Pull Request Checklist

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• Add any new Python packages to the METplus Components Python Requirements table.
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🤖 Generated with Claude Code

[jprestop]

I approve this PR to break out the Check Links in a new job in the documentation workflow.