Deprecate SimpleNIP46 as demo Compatibility Alias

[AustinKelsay]

Part of #154
Blocked by: #156

Goal

Document Full (NostrRemoteSigner*) as the production Public Facade and mark Simple (SimpleNIP46*) as demo/compat Compatibility Aliases deprecated for 1.0. Update NIP-46 README and module header comments; add @deprecated on Simple classes.

Acceptance

• README dual-architecture section states Full=production, Simple=demo/compat (deprecated for 1.0).
• SimpleNIP46Client and SimpleNIP46Bunker are @deprecated.
• Examples that intentionally use Simple note the demo status; no forced migration of every example in this ticket unless cheap.
• NIP-46 tests remain green.

Notes

AFK. Do not remove Simple in 0.x. Do not grow Simple APIs.

[AustinKelsay]

Implemented on feature/cleanup-tier-ab-api-surface and included in PR #163 targeting staging. Spec #154.