Documentation Check

This PR promotes the minimum-implicit-member experiment to GA: the experiment constant is removed, the elevation now lives on organization-workspace-access (attached via DefaultOrgMemberRoles), and the experiment gate on customizing default_org_member_roles is dropped.

Updates Needed

• docs/install/releases/feature-stages.md - Still lists minimum-implicit-member in the generated experiments table. This file is auto-generated; regenerate with make gen so the removed experiment no longer appears.
• docs/reference/api/schemas.md - The Experiment enum still includes minimum-implicit-member (line ~7227). Auto-generated from codersdk; regenerate with make gen.

New Documentation Needed

• docs/admin/users/ (e.g. groups-roles.md or organizations.md) - Customizing default_org_member_roles and the organization-workspace-access role ("Gateway Accounts") is now GA but undocumented. Consider documenting how organizations deviate from the default member roles and what the organization-workspace-access elevation grants.

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