Adds ci/build.sh + ci/bread-ecosystem.rev (pinned to bread-ecosystem
147cfbb) following the pattern proven in breadpad, so releases build
inside the shared pinned container instead of installing toolchain
deps directly on the bare runner. Routes dev/rc/release build+test
steps through it and adds a check.yml for fast clippy/test feedback
on feature/fix branches. No ci/deps.txt — breadcrumbs' dependencies
(clap/serde/toml/serde_json) are pure Rust with no system library
needs; nmcli/tailscale/sudo/xdg-open are shelled out to, not linked.
