v0.3.0 — agent-friendly
zai-usage check: machine gate for agent runtimes — exit 0 when quota left ≥--min% (default 10), 1 when low, 2 on error. Windows:5h(default),monthly-tools,weekly.--jsonemits{ok, left, used, callsLeft, resetsInMin}.--helpand--versionwork without an API key- 24 unit tests; agent-integration docs in README