Feature request: local historical per-model token usage (beyond current session)

/usage currently only shows the current session's totals, with no per-model breakdown and no way to see history across sessions. Session transcripts already exist locally under ~/.claude/projects/*/*.jsonl and record which model handled each turn — but they don't include per-call token counts, and there's no command to aggregate them.

Request: extend /usage (or add a new command) to report historical, per-model token usage aggregated from local session data across multiple sessions/days — similar to what the Console usage page shows, but usable by any individual user locally, without requiring a workspace Billing/Admin role or Admin API key (both currently required to see this on platform.claude.com/usage).

This would let individual developers understand their own usage patterns (e.g., cost breakdown across background subagents run at different model tiers) without needing organizational admin access.

Related: #1109 (different angle — visibility of current-session metrics for Max subscribers; this request is about historical, cross-session, per-model data for any user tier).