Please expand the current Authentication Standard specification to include the "Wire Protocol" (API contracts) and "Data Contracts" (Interfaces).

[hotlong]

This is crucial to ensure that any driver (better-auth, Auth0, etc.) implementing this spec provides a consistent API experience for frontend clients.

Please perform the following tasks:

1. Create Constants File (packages/spec/src/system/authentication-constants.ts):

   • Define and export an AUTH_CONSTANTS object.
   • It must include standard keys for API communication:
     • HEADER_KEY: Set to 'Authorization'.
     • TOKEN_PREFIX: Set to 'Bearer '.
     • COOKIE_PREFIX: Set to 'os_' (for consistent cookie namespacing).
     • CSRF_HEADER: Set to 'x-os-csrf-token'.

2. Create Types File (packages/spec/src/system/authentication-types.ts):

   • Define interface StandardUser: This represents the normalized user object that all drivers must return.
     • Required fields: id, email, emailVerified (boolean), createdAt, updatedAt.
     • Optional fields: name, image.
     • Allow index signature [key: string]: any for driver-specific extensions.
   • Define interface StandardSession:
     • Required fields: id, userId, expiresAt, token.
     • Optional fields: ipAddress, userAgent.

3. Update Exports (packages/spec/src/index.ts):

   • Export everything from the new authentication-constants.ts and authentication-types.ts files.

4. Update Documentation (docs/AUTHENTICATION.md):

   • Add a new section titled "API & Wire Protocol".
   • Document that all implementations MUST accept the standard Bearer token header.
   • Document the StandardUser interface, explaining that plugins/drivers must map their internal user representation to this standard interface.

5. Refinement:

   • Ensure the naming consistency with the existing authentication.zod.ts.