[byRandom]

Proposal #1 from the architecture review: one module owns everything that depends on the dimension.

Before

• Two Dimension enums, the finder's and the app's, with a conversion between them.
• The Nether and End level heights written inside StructureGenerator's three constructors.
• A TerrainRef enum and a BiomeLookup trait that only passed each call on to the right dimension's sources.
• The finder building its Nether and End sources by hand.
• The app's marker workers building all six biome sources and terrains for every seed, even when only one dimension was shown.
• The structures example skipping Nether and End sets by their names.

After

• New module mc_core::world.
• Dimension is a single enum, shared by the app and the finder. It provides:
  • id and from_id;
  • label;
  • level(), returning a Level (level range, sea level, generated range);
  • biomes();
  • has_set(set). Ruined portals belong to both the Overworld and the Nether.
• World::new(seed, dimension) owns that dimension's biome source and terrain. It provides:
  • biome and biome_at_block;
  • base_height and base_column;
  • strongholds();
  • structures(), the StructureGenerator for that dimension.
• StructureGenerator::new(&World) replaces new, nether and end; TerrainRef and BiomeLookup are removed.
• The finder builds the Nether and End worlds only when a filter needs them.
• The app's marker workers build one world per dimension the first time it is needed.

Net change: 130 lines added and 345 removed, plus the new module and its test.

Verification

• New tests/world.rs checks that:
  • World answers exactly like the sources it wraps (biomes, heights and columns in all three dimensions);
  • every structure set belongs to the right dimensions;
  • dimension ids survive a round trip.
• All parity tests now go through World, and they still pass.
• The structures example gives byte-identical output to main on three seeds.
• The app, run under a virtual display, shows the same map and markers as before.

No behaviour change, so no release.

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Generated by Claude Code