Expose Max plan usage limits via Claude Code API/SDK

Currently there's no programmatic way to check Claude Max plan usage limits (session %, weekly all-models %, weekly Sonnet-only %) from within Claude Code or the CLI.

The only option is to scrape claude.ai/settings/billing via a headless browser, which requires maintaining a separate browser session just for this purpose.

Request: Expose plan usage limits through a Claude Code built-in — either:

• A CLI command like claude usage that reads from a local/cached API endpoint
• A tool/context variable available to skills and commands during a session
• An authenticated REST endpoint that Claude Code can call with the existing session token

Use case: Power users building custom skills and commands (e.g. /limits that shows current rate limit status inline during a coding session) currently have no clean path to this data.