Fault-injecting our LLM provider to trust Bifrost fallbacks

TL;DR: We run an LLM-backed build-failure summariser at Buildkite. To stop a provider wobble from breaking it mid-deploy, I ran a game day that fault-injected OpenAI with 429s and 500s and watched whether Bifrost's fallback config actually rerouted. It did, but only after I fixed two things I'd set up wrong. We've got a small service that reads failed CI jobs and writes a one-paragraph summary into the build annotation, so engineers don't have to scroll 4,000 lines of test log to find the one a...