Run required docs check on every PR

[krowvin]

Summary

• run the Docs Validation workflow for every pull request
• retain the existing path filters for pushes to main

Why

The main - required checks ruleset requires the html job for every pull request. The workflow's pull-request path filter prevented that job from starting when a change did not touch documentation, Python source, project metadata, scripts, or CONTRIBUTING.md. GitHub then left the required html context in an indefinitely expected state and blocked otherwise valid pull requests.

Impact

Every pull request now reports the required html status. Scheduled behavior and path-filtered validation after pushes to main remain unchanged.

Validation

• actionlint -shellcheck= .github/workflows/docs.yml
• commit-time yamlfix and generated ownership checks
• confirmed the unrestricted pull-request trigger matches the repository ruleset's unconditional html requirement

actionlint with ShellCheck enabled still reports the existing SC2129 style warning in the workflow summary step; the same warning is present on origin/main and is outside this fix.