New /project command names the claude.ai Project for a session's usage reports

What

A new slash command, /project, sets which claude.ai Project a session's usage is reported under. Its description is "Set the claude.ai Project for this session's usage reports", and it takes [Project ID or claude.ai address] [--save] | clear [--save].

• Choosing a Project: you give a Project ID or a claude.ai/project address. --save stores it as attributionProject in your local settings, and clear removes it.
• Requirements: you must be logged in with claude.ai and connected directly to Anthropic, not in a cloud session, and CLAUDE_CODE_ATTRIBUTION_HEADER must not be set to 0. Managed settings can block the command, and the CLAUDE_CODE_ATTRIBUTION_PROJECT environment variable takes priority over it.
• Availability: the command only appears when an eligibility check passes and the remote flag tengu_gentle_cupcake is true. Nothing has been read about that flag. Its built-in fallback is false. The command also works in non-interactive sessions.
• Status lines: the session reports "This session names claude.ai Project ${r.name} for usage reports (${r.origin})" or "This session names no claude.ai Project for usage reports."
• Where the setting came from: the origin is now worked out in one shared place. The source 'harness' is shown as CLAUDE_CODE_ATTRIBUTION_PROJECT, and 'admin_default' as "your organization's default". The existing 'user' and 'project' settings labels are unchanged. A setting given with --settings is now shown as "attributionProject in --settings".
• Accepted IDs: the attributionProject setting now accepts IDs starting with "chan_" as well as "claude_proj_", and also the UUID of a claude_proj_ Project.
• Error text: a related error now says the session "is in a claude.ai Project" instead of "started inside a claude.ai Project".

Why

When the command is available, you can choose which Project your usage counts towards from inside a session, and keep that choice with --save. Usage can also now be reported under a new kind of Project, whose ID starts with "chan_".