Fix crash from unresolved auth on named-server connections

[isc-klu]

Summary

• Fixes Extension fails to activate, isfs files can no longer be opened #1837 — AtelierAPI.config/.active call this._config.auth.clone() unconditionally. For a named-server connection, _config.auth was populated from getResolvedConnectionSpec's fallback (the raw, unresolved intersystems.servers entry), whose auth is legitimately undefined until resolveConnectionSpec has run — causing TypeError: Cannot read properties of undefined (reading 'clone') and extension activation failure (breaking isfs file access).
• getResolvedConnectionSpec now always returns a spec with auth populated, and its dflt parameter is typed to match what's actually passed (a raw IServerSpec, not a fully-resolved spec) so this can't regress silently.
• Added a config() overload for "intersystems.servers" so callers get a real type instead of any.

Test plan

• tsc --noEmit, eslint, and webpack build pass.
• Confirmed fixed by the reporter of Extension fails to activate, isfs files can no longer be opened #1837, who installed a local build and verified isfs files open again.