By: Tom Sydney Kerckhove <syd@cs-syd.eu>
Dedupe flake outputs and tune NixCI dependency discovery - Expose each derivation under exactly one attribute (drop packages.bombadil alias and the checks.* that merely re-listed packages/devShells), so NixCI no longer schedules the same build under several names. - Add nix-ci.nix enabling synchronous dependency discovery, so the shared dependency derivation is built once, up front, instead of every job recompiling dependencies in parallel. Defer the expensive cross/test builds behind clippy to fail fast.