Create: Trade Depots build world tile

Put the build-world tile at:
config/create_trade_depots/build_world/chunktile.nbt

Optional builders template:
config/create_trade_depots/build_world/builders-template.nbt

Requirements:
- Vanilla structure block .nbt file.
- Expected footprint is 16x16 blocks, exactly 1 chunk by 1 chunk.
- The tile repeats once per chunk in X/Z in the build-world dimension.
- The saved Y size can vary; build_world_tile_y in the common config controls the bottom Y where the tile is generated.
- First pass supports block states from the structure. Entities and block entities are not part of the build-world tile generator yet.
- /place_template with no color places builders-template.nbt raw and unprocessed.
- /place_template green, red, blue, or yellow filters the template to that marker system plus cyan/brown support samples, then runs marker processing.
- Green processing includes lime facing markers.
- Yellow processing includes orange inset markers; orange is not a separate command target.
- /smooth <passes> runs the current yellow/orange smoothing algorithm over the 16x16 chunk tile containing the player.
- builders-template.nbt is not placed automatically when entering the build world.
- Manual /place_template commands snap to the chunk containing the player and place at that chunk's north-west/min XZ corner.

Commands:
/tradedepots buildworld enter
/tradedepots buildworld leave
/tradedepots buildworld place_template
/tradedepots buildworld place_template green
/tradedepots buildworld smooth 1

Config:
build_world = "dimension" enables the dimension command path.
build_world = "none" disables it.
build_world = "world" is reserved for the later custom world-preset pass.
build_world = "both" enables dimension support now and reserves world-preset support for later.
