errors.md example calls non-existent Lease.Contains

[nficano]

Category: docs Severity: major
Location: docs/guides/errors.md:93-93

What

Lease (src/Arcp.Core/Leases/Lease.cs) exposes only the Capabilities dictionary and a Get(string) method; there is no Contains method (verified by grep). ctx.Lease.Contains(...) does not compile.

Evidence

    if (!ctx.Lease.Contains(LeaseNamespaces.FsRead))
        throw new PermissionDeniedException("fs.read required");

Proposed fix

Use ctx.Lease.Get(LeaseNamespaces.FsRead).Count == 0 or ctx.Lease.Capabilities.ContainsKey(LeaseNamespaces.FsRead).

Acceptance criteria

• The example uses a member that exists on Lease and compiles.

[nficano]

Fixed in #77 (merged).