CI as Infrastructure

Not written yet. Questions to answer here: what a CI runner is and where it runs, how caching and artifacts differ and why conflating them makes pipelines slow, what makes a pipeline flaky and how flakiness is diagnosed rather than retried, how CI interacts with a hermetic build system like Bazel (remote caching, remote execution), what secrets handling in a pipeline has to guarantee, and what it means to treat developer experience on the pipeline as the product.