docs: Document single-PR deployment limitation and production workaround

[Copilot]

The README documented staging aggregation strategy but didn't clarify whether individual PRs can be deployed to staging in isolation for testing.

Changes

• Staging Deployment section: Added note that staging always aggregates all open PRs, no single-PR isolation available
• Manual Single-PR Deployment section: New section documenting:
  • deploy.yaml supports workflow_dispatch with pr_number input
  • Deploys to production (forrt.org), not staging
  • Recommended only for emergency fixes; use aggregated staging or local testing for regular PR review

Key Clarification

# deploy.yaml supports manual PR deployment but targets production
on:
  workflow_dispatch:
    inputs:
      pr_number:
        description: 'PR number to deploy (optional, for manual testing)'
        # Deploys to gh-pages (production), not staging

No single-PR staging deployment exists. Staging always shows combined state of all compatible open PRs.

---

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[LukasWallrich]

@richarddushime can we change the individual PR deploy to go to staging? Or does copilot get the documentation wrong?

[richarddushime]

@richarddushime can we change the individual PR deploy to go to staging? Or does copilot get the documentation wrong?

the documentation by copilot is right , No single-PR staging deployment exists.Staging will always shows combined state of all compatible open PRs.,

Allowing a single PR deployment is what we are avoiding because the rest of the PRs changes wont be previewed on stagging site.
I also added a queue incase multiple PR s are running workflows to put on wait
and this will allow all PRs to deploy in order

[richarddushime]

This Documentation details would be nice if goes under contributing guidelines not in the main Readme file