[FEATURE] Display token usage (session + weekly) in the agent view row

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When running multiple background agents via claude agents (the agent view / FleetView), there is currently no way to see how many tokens each session has consumed. Users who build agents that track their own token usage (session or weekly) have no way to surface that information in the agent list view — the row summary is auto-generated by a Haiku model and there are no custom status fields available.

This makes it hard to monitor cost and usage across parallel agent sessions without opening each one individually.

Proposed Solution

Add optional token usage metadata to the agent view row — either:

1. Native field: Expose session_tokens and/or weekly_tokens as a standard column or badge in the agent list (similar to how PR status is shown), automatically populated from the session's actual usage.
2. Custom status field: Allow agents to programmatically set a short status string (e.g. via a slash command or SDK call) that appears alongside the auto-generated summary in the row.

Option 1 would require no changes from agent authors and would benefit all users. Option 2 is more flexible and could be used for any kind of agent-defined metadata beyond token usage.

Use Case / Motivation

• Users running many parallel agents (e.g. via /loop or routines) want to quickly see which sessions are close to their weekly token budget.
• Teams using Claude Code in an organization context want visibility into token consumption per task without leaving the agent list.
• Agent authors who already compute usage internally have no way to push that information to the UI.

Current Workaround

Printing token usage in the agent's text output and reading it via the peek panel (Space key). This is fragile and requires opening each session.

Additional Context

This feature request was created automatically via Claude Code (claude-sonnet-4-6) on behalf of a user who encountered this limitation while building agents that track their own session and weekly token usage.