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",

src/dsl/grammar/app.rs

@@ -174,6 +174,10 @@ const fn build_rebuild(_path: &MatchedPath, _source: &str) -> Result<Command, Va
     Ok(Command::App(AppCommand::Rebuild))
 }
 
+const fn build_version(_path: &MatchedPath, _source: &str) -> Result<Command, ValidationError> {
+    Ok(Command::App(AppCommand::Version))
+}
+
 const fn build_undo(_path: &MatchedPath, _source: &str) -> Result<Command, ValidationError> {
     Ok(Command::App(AppCommand::Undo))
 }
@@ -294,6 +298,14 @@ pub static REBUILD: CommandNode = CommandNode {
     hint_ids: &["rebuild"],
     usage_ids: &["parse.usage.rebuild"],};
 
+pub static VERSION: CommandNode = CommandNode {
+    entry: Word::keyword("version"),
+    shape: EMPTY_SEQ,
+    ast_builder: build_version,
+    help_id: Some("app.version"),
+    hint_ids: &["version"],
+    usage_ids: &["parse.usage.version"],};
+
 pub static SAVE: CommandNode = CommandNode {
     entry: Word::keyword("save"),
     shape: SAVE_AS_OPT,

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),