Config parsing, duplicate UUIDs, error layers, wrong layer types, and default config behavior.
Test plan: 03-config.md
Same UUID appears twice. Both should appear in legend with unique paths.
Contains: invalid geoviewLayerType, bad URL, and a valid service with a non-existing sublayer ID (partial loading). Notifications should appear for errors.
All config UI properties omitted — viewer applies defaults.
Explicit empty arrays — no tabs, no navbar buttons should render.