feat: add Codex usage telemetry

[catwithtudou]

Summary

• Add a Codex usage endpoint that reads local token_count events from Codex session JSONL files
• Add a current usage endpoint so the Usage page renders the active agent provider without querying Claude in Codex mode
• Update the Usage page to show Codex rate-limit windows, reset times, token usage, and unavailable states

Notes

Codex usage is best-effort local telemetry from session logs, not official billing usage. If CODEX_HOME or ~/.codex does not contain token_count/rate_limits events, the endpoint returns an unavailable state instead of failing.

Test Plan

• FEISHU_APP_ID=test FEISHU_APP_SECRET=test bun test
• FEISHU_APP_ID=test FEISHU_APP_SECRET=test bun run check
• bun run build:js
• bun run build:bin
• curl http://localhost:1985/api/usage/current against a minimal local usage route server

[catwithtudou]

Screenshot of the Codex usage telemetry UI: