Update Resource Groups docs for the redesigned UI - #2751

Note

Low Risk
Documentation-only changes with no runtime or security impact; accuracy fixes reduce misconfiguration risk for admins.

Overview
Updates Team & Enterprise Resource Groups documentation to match the redesigned org settings UI—markdown only; screenshots were re-uploaded to the documentation-images dataset under new hub asset names.

Getting started now walks through the group page’s four tabs (Overview, Resources, Users, Settings), retargets screenshots (overview, add-resources modal), drops the old “move repo” image, and adds descriptive alt text across pages including enterprise-resource-groups.md.

Auto-join and Spend limits instructions point at the Settings tab (Auto-include org members, spend limits card) with new screenshots; auto-join scope is reframed around the Include no_access members checkbox.

Behavioral corrections: Read+ creation excludes no_access org members; granular feature access is documented as a who gate org-wide, not a requirement that resources live in allowed groups; Jobs billing uses resource_group_id (plus org namespace), not namespace alone.

Copy edits: bold key terms, code role names, UI-aligned labels (Write+, Contributor+), and clearer Resources/Members bullets.

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