Chaos-TDD Fault Injection

Chaos-TDD for LLM agent pipelines — deterministic fault injection at existing seams, where the fault-injection test states the desired guarded behavior FIRST and the minimal production guard lands in the same PR. Use when hardening a pipeline against LLM/external-I/O fault families (truncated output, timeouts, 429s, wrong-shaped-but-parseable JSON, flapping backends), when building a fault catalog from operational bug history, when adding property-based fuzz over LLM output shapes, or when reviewing whether a pipeline's failure paths abstain with reason codes instead of degrading silently. NOT for infra-level chaos on distributed systems (chaostoolkit/toxiproxy are the ri…