Add Aegis SDK role permission guard

[El-swaggerito]

Description

Difficulty: Expert

Type: Feature

Summary

Add a role permission guard for SDK operations.

Current Behaviour

SDK methods may not consistently distinguish read-only, investor, issuer, compliance operator, and admin capabilities.

Expected Behaviour

The SDK should guard privileged operations and return typed permission errors.

Suggested Implementation

Create role types, guard utilities, method integration, tests, and docs.

Files or Areas Likely Affected

• src/client/
• src/admin/
• src/compliance/
• src/errors/
• tests/
• docs/

Acceptance Criteria

• Role permission guard is implemented.
• Read-only and privileged operations are distinguished.
• Admin-only operations are protected.
• Typed permission errors are returned.
• Tests cover supported and unsupported roles.
• Docs explain permission assumptions.

Additional Notes

This is security-sensitive SDK work.

[Carlys17]

I'd like to work on this. I'll add role types (read-only/investor/issuer/compliance/admin), a guard utility that protects
privileged SDK methods, typed permission errors, and tests covering supported and unsupported roles plus docs.