The ADR-0054 version guard piped `nix develop -c cargo metadata` to node,
but the flake devShell prints a banner to stdout — corrupting the JSON
pipe, so the guard aborted under `set -e` and the v0.2.0 release failed
there (before building anything). Replace it with a toolchain-free
`grep -m1 '^version = ' Cargo.toml` (the anchor excludes dependency
`version =` keys). No real version mismatch occurred — the tagged commit
has version 0.2.0.
Cargo.toml version is the single source of truth, surfaced by a
--version/-V CLI flag and an in-app `version` command (both via
cli::version_text -> cli.version_line). release.yaml gains a guard that
fails the release unless the v* tag equals v<CARGO_PKG_VERSION>, keeping
--version, the release name, and the asset in lockstep. New app command
wired across grammar/REGISTRY/dispatch/usage/help/hint-corpus/keys; 6
test-first tests. Also fixes a stale "macOS deferred" comment in
release.yaml. ADR-0054 + README index + plan-doc step 1.