feat(cli): --version/-V + in-app version command + release guard (ADR-0054)

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.

src/dsl/grammar/mod.rs

@@ -791,6 +791,7 @@ pub static REGISTRY: &[(&CommandNode, CommandCategory)] = &[
     (&app::QUIT, CommandCategory::Simple),
     (&app::HELP, CommandCategory::Simple),
     (&app::HINT, CommandCategory::Simple),
+    (&app::VERSION, CommandCategory::Simple),
     (&app::REBUILD, CommandCategory::Simple),
     (&app::SAVE, CommandCategory::Simple),
     (&app::NEW, CommandCategory::Simple),