cache-tax README: the standalone status line row up top

[karanb192]

Summary

A reader on 18 Sep pulled cache-tax.js out of the repo and calls it with --statusline from his own status line script, with no plugin install, and said that path was buried under the plugin sections. This moves the standalone status-line use up to a section near the top of plugins/cache-tax/README.md, titled by what the reader gets.

Details

New section, second in the file, before Install: "A cache countdown row in a status line you already have".

• Says no plugin install is needed and that the script is one dependency-free file.
• The exact commands: a curl of the raw file to ~/.claude/cache-tax.js, and the one line to call it from an existing status line script with the same stdin Claude Code piped in.
• The two rows it prints, warm and cold, the same figures the Status line segment section already quotes.
• That it reads the native prompt_cache object (v2.1.251+) so Claude Code re-runs it when the cache goes cold, and falls back to the transcript named in the payload on older versions.

Nothing else in the README changes; the Status line segment section further down still covers the marketplace-clone path.

No version bump: the plugin's shipped files are unchanged, and the earlier README-only changes to this plugin (#54, #63, #64) did not bump plugin.json.

Test plan

Ran the documented command against a status-line payload in the worktree and got the documented row shape for both states:

cache 46m left · 219k · cold costs $4.37 · last miss ttl_expired_1h
cache COLD · next msg re-writes 219k = $4.37 · last miss ttl_expired_1h

npm test:

ℹ tests 1929
ℹ pass 1929
ℹ fail 0