[MNT] maintenance & integration plan GC.OS

[fkiraly]

pygam has joined GC.OS, this issue outlines integration into an umbrella maintenance model.
This issue is to plan urgent maintenance items and handover.

Community input on todos and wishlist is also appreciated, e.g., what are "burning" items, suggested priorities.

Maintenance items

• pyproject review, dependabot PRs
• migrating project packaging to simple pip
• python 3.11-3.13 compatibility [MNT] additional python 3.13 compatibility actions #372
• EOL for python 3.8 [MNT] additional python 3.13 compatibility actions #372
• newer scipy compatibility [MNT] compatibility with scipy>=1.14.0 and python 3.13 #366
• newer scikit-learn compatibility, stringent testing using scikit-learn estimator tests
• dependency review - is progressbar2 needed?
• stale PR review and triage - highest priority
• failing docs
• test that tutorial notebooks run, fix any breakage
• optional: resume conda releases https://github.com/conda-forge/pygam-feedstock [MNT] fix conda feedstock #395

handover items

• issue triage
• bugfixing board - tagging bugs and moving to board
• stale PR review and triage - all
• operational handover
• pointers to dev channels
• digital assets
• release pipeline

roadmap items for consideration or wishlist

• test coverage review (not just line coverage but case coverage)
• big additive models
• skpro interface [ENH] skpro interface #403