Meshtastic was UI-filtering only (no meshtastic data backend). Drop it as a
node type/option, and simplify the map marker/cluster/popup rendering now that
every node is meshcore. Update product copy to MeshCore-only. The nodeTypes
query plumbing stays (the unified view's type is always 'meshcore').
Production build passes.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>