Endpoint discovery during node interview

[dfederm]

Update the node interview process to discover Multi Channel endpoints and interview their command classes.

Scope:

• After NIF processing, check if MultiChannel CC is in the supported list
• If supported: send EndPointGet to discover count and capabilities (identical/dynamic flags)
• For each endpoint: send CapabilityGet to get device class + supported CC list
• Create Endpoint instances and populate their CC dictionaries via CommandClassFactory
• Interview CCs on each endpoint (reusing existing dependency-ordered interview logic)
• For the "identical endpoints" optimization: query only endpoint 1 and clone capabilities to others

Design notes: The interview dependency system already exists (InterviewDependencies). Multi Channel CC should be interviewed early (before application CCs) since it creates the endpoints that other CCs live on.

Depends on: Issues #136, #137, #138