feat: add pre-registration conformance test (#120)

* feat: add pre-registration conformance test

Add conformance test for OAuth pre-registration flow where the server
does NOT support Dynamic Client Registration (DCR) and clients must
use pre-configured static credentials.

This addresses issue #34 (Client Registration Methods) - specifically
the pre-registration section that was previously not covered.

Changes:
- Add disableDynamicRegistration option to createAuthServer helper
- Add auth/pre-registration scenario with pre-registered client creds
- Add MCP_PREREGISTRATION spec reference
- Add context schema for pre-registration credentials
- Add withOAuthRetryWithProvider helper for pre-configured providers
- Add negative test client (auth-test-attempts-dcr.ts) that ignores
  pre-registered credentials and fails

The scenario verifies that when a server does not advertise
registration_endpoint in its OAuth metadata, compliant clients
use pre-registered credentials passed via context instead of
attempting DCR.

Closes #34

* fix: add redirect_uris to saveClientInformation call

* chore: remove unused WithOAuthRetryOptions interface

src/scenarios/client/auth/spec-references.ts

@@ -72,5 +72,9 @@ export const SpecReferences: { [key: string]: SpecReference } = {
   SEP_1046_CLIENT_CREDENTIALS: {
     id: 'SEP-1046-Client-Credentials',
     url: 'https://github.com/modelcontextprotocol/ext-auth/blob/main/specification/draft/oauth-client-credentials.mdx'
+  },
+  MCP_PREREGISTRATION: {
+    id: 'MCP-Preregistration',
+    url: 'https://modelcontextprotocol.io/specification/2025-11-25/basic/authorization#preregistration'
   }
 };