MTR Map Overlay

- **JourneyMap now has the full rail and route layer.** Its fullscreen map draws sampled physical rails and adjacent colour bands for routes sharing a rail. Independent TRACKS and ROUTES buttons use the same red/off and green/on icon convention as Xaero. With both enabled, routes sit over tracks; station and platform icons remain on top in every switch combination.
- **Map-anchored rendering.** JourneyMap uses Xaero-matched screen-pixel track width and the map's live pan, drag and zoom projection. The path and landmark layer stays aligned while dragging instead of floating or tearing.
- **Lighter rendering and data handling.** Route paths reuse sampled track geometry; rail bounds cull offscreen work on both maps; JourneyMap batches compatible icons. Snapshot chunk assembly validates order, size and metadata, and client fallback caches are cleared when changing servers.

Minecraft 1.21.1, MTR 4.1.0-beta.2, and the v5 network snapshot protocol remain unchanged. Install only the JAR matching your loader. For whole-network data, the matching mod must run on the server as well as the client; client-only use is limited to MTR's nearby data.