#416 Add VaultAnnotationProvider support to @swamp/1password

Problem

swamp now supports first-class vault annotations via swamp vault annotate and swamp vault inspect (swamp-club#412, PR #1434). The VaultAnnotationProvider interface allows vault providers to store metadata (URL, notes, labels) alongside secrets. The built-in local_encryption provider already implements it.

The @swamp/1password extension does not yet implement VaultAnnotationProvider, so swamp vault annotate returns an error for 1Password vaults.

Proposed solution

Implement VaultAnnotationProvider on the 1Password vault provider:

• url → 1Password item URL field
• notes → 1Password notesPlain field
• labels → 1Password custom labeled fields

The createProvider factory should return an object implementing both VaultProvider and VaultAnnotationProvider. No schema or adapter changes needed — swamp detects annotation support at runtime via duck typing.

This was the original motivating use case from swamp-club#412 — the issue author specifically wanted to annotate a GitHub App private key PEM stored in a 1Password vault.

Alternatives considered

None — this is the natural extension of the core annotation feature to the 1Password backend.