Adds the Corridor world type (世界类型：走廊) for Minecraft 26.3 (Fabric).
An endless one-chunk-wide slice of normal terrain, in all three dimensions:
Width: exactly one chunk (x = 0..15)
Length: infinite along the Z axis
Height: full dimension height (overworld -64 .. 319, nether/end 0 .. 255)
Barrier walls at x = 0/15 for the full height; floor and ceiling are open
Inside the corridor, terrain generates exactly like a normal world: noise terrain, biomes, carvers, structures, features and natural mob spawns (overworld: vanilla overworld generator settings + multi_noise overworld biomes; nether: vanilla nether settings; end: vanilla end settings + end biome source)
Everything outside the corridor is empty void — no terrain, no structures, no features
Nothing crosses the barrier walls: feature/structure block writes and worldgen entity spawns outside x = 1..14 are clipped (e.g. end obsidian pillars are cut at the wall)
No experimental-features warning on world creation
The corridor appears in the world type list next to Default/Superflat/Large Biomes/Amplified/Single Biome. World spawn is moved onto dry land inside the corridor near (8, surface, 8) on server start. Barriers are never a valid spawn/respawn surface.
In the End, everything is pulled inside the corridor:
The arrival obsidian platform is built at (8, island surface, 12) instead of (100, 50, 0)
The dragon fight (exit-portal altar, dragon, egg) is centered on x = 8 instead of x = 0, the dragon's flight-path node rings are squashed into the corridor so it circles the altar and descends to perch instead of spiraling upward forever, and the post-kill gateway ring is squashed onto an ellipse inside the corridor (x = 4..12, z = ±64) so every gateway hovers above the main island
Gateways teleport to real outer-island terrain inside the corridor: the exit is searched along z (1024..8192) via noise-only height queries, and a paired return gateway is spawned on the island, mirroring the vanilla flow
Gateway landings are sanitized: the vanilla "tallest block within 5 columns" scan would pick barrier wall tops (barrier is full-face and not bedrock) or the void past the island edge, so unsafe landings are redirected to main-island ground; outward landings use the noise-found surface directly
Obsidian pillars whose center falls in chunk x = 0 generate normally but are clipped at the barrier walls; pillars outside the corridor never generate
