The `cube` binary (REPL + script runner over one shared CubeStore) is
now its own crate at `cubecli/`, matching the spec's package outline
that lists cubecli as a separate crate from the composition layer.
What changed:
- New `cubecli/` crate with `Cargo.toml` (deps: cubecoords, cubestore,
cubefs, cubecode, cubecrypt, cubesys) and `src/main.rs` (copy of
the former `cubesys/src/bin/cube.rs`).
- `cubesys/Cargo.toml`: removed the `[[bin]]` entry for `cube`; keeps
`cube-demo`, `cube-server`, and `cubec` as before.
- `Cargo.toml` (workspace): added `cubecli` to members.
- `cubesys/src/bin/cube.rs` removed (code now lives in cubecli).
The `cube` binary is unchanged: same CLI surface, same demo, same
commands. The `cube-demo` binary in cubesys still wraps
`cubesys::demo::run()` and is unaffected.
Verification: `./check` gate passes (fmt + tests + clippy -D warnings);
`cube --help` and `cube demo` both work.
Co-Authored-By: Hermes Agent
CUBELinux-2