storage key prefix — keep the historical prefix of the call site so previously persisted restore points remain readable.
Look up restorePoint; if absent, persist currentToken under it
(creating the restore point for a future reload) and report none.
If present, check the server: signed returns the signed object and
removes the restore point, pending returns the token so the caller
can resume waiting.
Persistence of RequestTokens keyed by a caller-chosen restore point identifier (e.g. a hash of document + page URL), so a signing session survives page reloads.
Use case: the user starts signing and switches to the Autogram mobile app; the OS suspends the browser and the page reloads on return. With a restore point, the page detects the document was already signed and completes without user interaction.