Documents pipeline architecture, how to run it, WFE features demonstrated, preflight tool checks, and graceful infrastructure skipping. Adds nextest cover profile for llvm-cov integration.
Root README covers architecture, Rust builder API quick start, YAML pipeline quick start, provider table, deno executor overview, feature flags, and testing instructions. Per-crate READMEs follow consistent structure: one-liner, what it does, quick start code example, API reference, configuration, testing, license. Engineering-confident tone throughout.
