The post-install hint printed at the end of a RevenueCat run. Returns the
empty string when no Apple key was provided (the user picked n), so the
hint is silently omitted for Android-only setups. Pulled out of iap()
so the conditional is testable.
Validates the CLI invocation and returns the parsed command name (auth
or iap). Returns null for any other shape — the caller is responsible
for printing a usage hint and exiting with a non-zero status code.
Builds the slate plan for an iap invocation. Mirrors planAuthSlate in
shape; for RevenueCat the user can type n to skip a platform key, which
is normalised to the empty string (the stub treats '' as "leave the
configure line commented out with placeholder text").
Callback used by the planners to read a single line of user input. The
runtime wires this to a CliDialog text question; tests substitute a
canned-answer recorder.