v1.3.27 — Unavailable backend handling

I added focused handling for inaccessible backends: distinguish observed client behavior from unknown server logic, select an explicitly labeled local substitute, supplied finite replay or deferred integration, and keep hard real-service requirements pending until verified.

The new runnable synthetic notes example uses the existing checker, with 23 frozen scenarios for local save/reopen, unavailable versus empty, malformed responses, replay mismatch and pending synchronization. Six deliberate misleading structured completion/observation mutations are rejected. This source-exposed same-agent example makes no live-provider, remote-persistence or production integration claim.

Installation, optional updates, consent, safe paths, recovery and existing compatibility behavior remain unchanged. The release updates skill guidance and adds a conditional reference without new dependencies or services.