DOC Create triage guide in maintainer documentation

As part of talking about triaging at the Scientific Python Summit I realised that we have quite some cumulative experience with triaging. There are also different approaches to things.

As a result I think it would be useful if we create a triaging guide as part of our developer/maintainer documentation. The goal of the guide would be to serve as a reference for what to do as a triager, what tools we have available to help with the process and so on.

Some initial things I can think of including:

• list of labels we have for triaging and what to use them for
• "please don't open a PR before the discussion has converged" as a policy (triagers should close these "early PRs" to help enforce this)
• bookmarked search queries/lists of issues
  • needs triage
  • new PR without reviews
  • new PR without reviews by a maintainer
    • needs more maintainer usernames in the query
    • we could have a similar query for recurring contributors, but how?
  • PRs waiting for second reviewer
  • Open PRs that you have reviewed in the past
  • look at PRs marked with "autoclose" and decide to potentially remove the label or re-open if the PR has significantly improved scikit-learn/scikit-learn/issues (sort:updated-desc label:autoclose)
• integrate with https://scikit-learn.org/dev/developers/bug_triaging.html#triaging-operations-for-members-of-the-core-and-contributor-experience-teams

Can you think of more search queries that would be useful @lesteve?

xref https://github.com/scientific-python/summit-2025-nov/issues/6

Start with the existing developer/maintainer documentation, especially the bug_triaging.html#triaging-operations-for-members-of-the-core-and-contributor-experience-teams section, and review the linked GitHub search queries. The guide should cover triage labels, early-PR policy, useful searches, autoclose handling, and integration with the existing operations documentation.