Validate the example commands embedded in shortcut definitions (the
"Example: lark-cli ..." lines in each shortcut's Tips, shown in --help)
against the real command tree built by cmd.Build. Implemented entirely as
test-only code in cmd/ (package cmd_test), so it ships in no binary and is
not importable by product code; the truth source is cmd.Build, the same
tree the binary uses, so the check cannot drift. It runs in the standard
unit-test CI job (go test ./cmd/...); a renamed command or unaccepted flag
in an example fails that job.
