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/command.rs

@@ -557,6 +557,10 @@ pub enum AppCommand {
     /// (the buffer is empty post-submit). The live-input surface is
     /// the F1 keybinding, handled in `App::handle_key`, not here.
     Hint,
+    /// Print the application version (ADR-0054): the in-app twin of the
+    /// `--version` / `-V` CLI flag. Emits `CARGO_PKG_VERSION` — the same
+    /// single source of truth — into the output panel.
+    Version,
     /// Rebuild `playground.db` from `project.yaml` + data/, with
     /// confirmation modal.
     Rebuild,
@@ -1019,6 +1023,7 @@ impl Command {
                 AppCommand::Quit => "quit",
                 AppCommand::Help { .. } => "help",
                 AppCommand::Hint => "hint",
+                AppCommand::Version => "version",
                 AppCommand::Rebuild => "rebuild",
                 AppCommand::Save => "save",
                 AppCommand::SaveAs => "save as",