Cross-API consistency issues between sim-swap and sim-swap-subscriptions

[hdamker]

Problem description

Cross-API consistency issues between sim-swap.yaml and sim-swap-subscriptions.yaml, none blocking on its own:

1. Error codes for the same identifier-resolution outcome differ: subscriptions' 403/422 include INVALID_TOKEN_CONTEXT/UNSUPPORTED_IDENTIFIER; sim-swap's don't.
2. Subject vocabulary: subscriptions' section header and text say "device"; sim-swap's header says "phone number" but its own 422 examples say "The device cannot be identified."
3. CreateSubscriptionBadRequest400.code still lists INVALID_TOKEN, but its example (GENERIC_400_INVALID_TOKEN) was removed.
4. Three id styles in sim-swap-subscriptions.yaml: SubscriptionId.example (qs15-h556-rt89-1298), operation examples ('1119920371'), and the new Subscription schema example (UUID 550e8400-…).
5. Casing: info.title "SIM Swap" vs "Sim Swap Subscriptions"; tags follow the same split.
6. sim-swap defines latestSimChange inline with a duplicated RFC 3339 reference; sim-swap-subscriptions has a reusable DateTime schema.

Expected action

Address when the definitions are next edited.

Additional context

Raised during Release Management review of the r4.1 rc snapshot (#283).