[FEATURE] Team/org-level /stats view (UI + terminal) for admins

Problem / use case

/stats today is per-user and only renders in the interactive client, so a team lead has no way to see the team's Claude Code usage without each member manually screenshotting their own card. As a Team plan Owner I want an aggregate view of my team's usage.

Proposed

1. An org/team usage view in the claude.ai UI for Owners/Admins that rolls up the /stats metrics (tokens, sessions, active days, model mix) per member; and/or
2. a claude /stats --team (or --org) variant in the terminal for admins.

Context: the Team plan has no usage API today (the Analytics API is Enterprise-only), so this fills a real gap for Team-plan admins.