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/friendly/strings/en-US.yaml

@@ -162,6 +162,10 @@ error:
 # ---- Help text (CLI banner + in-app `help` command) ------------------
 # ---- CLI argument-parsing errors (stderr before TUI starts) ---------
 cli:
+  # Version line for `--version` / `-V` and the in-app `version` command
+  # (ADR-0054). `{version}` is `CARGO_PKG_VERSION` — the single source of
+  # truth, equal to the `v*` release tag (release CI guards the match).
+  version_line: "rdbms-playground {version}"
   missing_value: "missing value for --{flag}"
   invalid_value: "invalid value for --{flag}: {value} (expected one of: {expected})"
   unknown_argument: "unknown argument: {arg}"
@@ -186,6 +190,7 @@ help:
 
     Options:
         -h, --help               Print this help and exit.
+        -V, --version            Print the version and exit.
             --theme <light|dark> Override theme (default: auto-detect).
             --data-dir <PATH>    Use PATH as the data root instead of
                                  the OS-standard location for this run.
@@ -210,6 +215,7 @@ help:
 
     App-level commands (typed inside the app, available in both modes):
         quit                     Exit cleanly.
+        version                  Print the application version.
         mode simple|advanced     Switch input mode.
         help                     Show this list of commands in-app.
         save                     Save the current temp project under a
@@ -258,6 +264,8 @@ help:
         help <command>             — detailed help for one command (e.g. `help insert`)
     hint: |-
         hint                       — explain the most recent error (press F1 for a hint on what you're typing)
+    version: |-
+        version                    — print the application version (same as the `--version` command-line flag)
     rebuild: |-
         rebuild                    — rebuild the project database from project.yaml + data/ (with confirmation)
     save: |-
@@ -425,6 +433,9 @@ hint:
     hint:
       what: "Explain the most recent error — or, pressing F1 while typing, the command you're building."
       example: "hint"
+    version:
+      what: "Print the application version."
+      example: "version"
     rebuild:
       what: "Rebuild the project database from its saved text files."
       example: "rebuild"
@@ -874,6 +885,7 @@ parse:
     quit: "quit"
     help: "help [<command>]"
     hint: "hint"
+    version: "version"
     rebuild: "rebuild"
     save: "save  |  save as"
     new: "new"