Repo Map

What each top-level directory holds. The packages/ breakdown is kept in one place, the “Directory map” in RFC-0001, and check-package-directories checks it against the tree, so it is not repeated here.

Directory	Holds
`packages/`	Every crate and C port: language APIs, core, RMW backends, platforms, boards, drivers, CLI, runners, tooling, tests, verification. See RFC-0001’s directory map.
`examples/`	Standalone copy-out projects, shaped `examples/<platform>/<language>/<example>/`. The RMW is chosen at build time.
`book/`	The nano-ros Book (users and porters), plus `page-map.toml`, which records which book and part every page belongs to.
`book-internals/`	This book.
`docs/`	The records: `design/` (RFCs), `roadmap/` (phases), `issues/`, plus `development/`, `reference/` and `research/`.
`just/`, `justfile`	Build orchestration. `just/check/*.just` holds the gates, and the fast lane is derived from those recipes.
`scripts/`	Generators (`gen-`), gates (`check-`, `scripts/check/`), probes (`scripts/probe/`) and shared helpers (`scripts/lib/`).
`cmake/`	The CMake road: `find_package(NanoRos)` support, board CMake and ament-surface shims.
`zephyr/`	The Zephyr module (west road), with its Kconfig generated from the knob registry.
`integrations/`	Glue for host tools that are not nano-ros’s own build: FreeRTOS, NuttX, PlatformIO, PX4, S32DS.
`config/`	Toolchain and target lists, and per-family defaults.
`templates/`	Scaffolds for out-of-tree boards and cargo-zephyr projects.
`tests/`	Shell and CMake fixture tests. The Rust integration tests live in `packages/testing/nros-tests`.
`docker/`, `ci/`	Container images for development and CI.
`locks/`	Registry lockfile pins.
`third-party/`	Provisioned SDKs and RTOS sources (gitignored; `nros setup` fills it).
`tools/`	The host environment and the pinned Rust toolchain for tools.
`changelog.d/`	towncrier fragments, one per change.