[draft] Add OSM/Arnis-style city feature prototype

[amithyst]

Summary

This is a draft prototype for bringing Arnis-style real-world city detail into Tellus without importing pre-generated region files.

The branch adds:

• a neutral external feature layer for roads, buildings, areas, lines, and points
• a cache-first Overpass/OSM source with local raw JSON cache, endpoint probing, cache estimation, and bounded prefetching
• OSM/Arnis-style city rendering details: tagged road widths/surfaces/lanes/sidewalks, bridge rails, tunnel shells, railway/barrier/water/landuse/leisure/natural surfaces, parking lots, street furniture, small POIs, entrances, and city-scale vegetation
• building metadata improvements for material/color/roof tags, storefront facades, and roof height handling
• Arnis-inspired deterministic tree shapes for wild trees and OSM natural=tree nodes
• an in-game map waypoint/teleport UI prototype for Earth worlds
• docs tracking the integration approach and Arnis parity status

Why

Tellus already owns the realtime Earth terrain generator, projection, tile caches, and chunk lifecycle. Arnis has useful OSM-to-Minecraft city-detail rules, but its implementation is an offline/export-style generator. This prototype ports the ideas into Tellus' chunk generator so features can be generated live from cached OSM/Overpass data while preserving Tellus terrain ownership.

Notes for maintainers

This is intentionally opened as a draft because the diff is large and likely needs to be split before review. The most upstreamable first slice is probably the neutral external feature model plus the cache-first Overpass source. Some UI/default naming still reflects the local WLB test workflow and can be renamed or removed before a final PR.

Network behavior is cache-first by default with bounded session fetches, so cached areas do not re-download data. Runtime toggles are available for disabling Overpass, forcing cache-only mode, limiting session network tiles, or changing endpoints.

Validation

Validated locally with:

GRADLE_OPTS='-Xmx4g' ./gradlew --no-daemon :mc1201:test :mc1211:test :mc1201:build :mc1211:build

The active 1.20.1 test jar was also exercised in a large Forge/Connector modpack enough to catch and fix a bridge-edge bounds crash in chunk generation. mc261 files were kept roughly in parity for settings/UI pieces but were not part of the final build validation in this branch.

[graperpie]

hi there, this looks super interesting but could you if possible show some screenshots on how this looks? (also use DH if possible otherwise it's okay), im looking to make a build of this myself sometime in the future