release: 2.0.91 — #135 context crash fix + #134 PostAuth proto body + #137 proxy parse + cache switch

- P0: ReferenceError context is not defined in streamResponse (#135)
- PostAuth empty proto body + X-Devin-Auth1-Token + Referer (#134 via @Await-d PR #144)
- parseProxyUrl whitespace + frontend error check (#137)
- RESPONSE_CACHE_ENABLED env (PR #142 by @suhaihui-git)
- IP rate-limit circuit breaker (#132)
- CLAUDE.md for agent rules