PlaceRuinedPortalPiece runs the template through the decoded processor
stack — positional Legacy streams per cell drive the gold-to-air,
lava-to-magma, netherrack-to-magma and block-age mossiness rolls, the
features-cannot-replace guard skips protected cells, and template lava
stays when it lands in existing lava. Drip columns below the portal
draw from a documented approximation of the shared decoration stream;
spreadNetherrack is not needed for the underground setups.
The placement chain is now proven end to end: chunk (1,0) reproduces
vanilla's saved start (portal_6, CLOCKWISE_90, NONE, air pocket at
(16,12,0)) and the fixture parity ticks up to 98.033% with biomes and
heightmaps still exact. generatorVersion bumps to 23.
Ports MonsterRoomFeature from bytecode with vanilla draw order and loop
structure: shell validation (solid floor and ceiling, one to five open
side columns), interior cave_air carving, cobblestone walls with the
mossy three-in-four floor roll drawn only where vanilla draws it, chest
placement faced away from its single opaque neighbour with the loot-seed
long consumed even though block entities are not modelled yet, and the
spawner's one-draw mob pick. Writes go through Feature.safeSetBlock
semantics against #minecraft:features_cannot_replace, captured verbatim
from the jar into the embedded datapack data.
The pass slots between geodes and the ores so the rooms' cave_air
pockets exist before ore ellipsoids roll their air-exposure discards.
The committed fixture's four chunks happen to contain no dungeons, so
measured parity holds at 98.028%, but the generator's output can differ
elsewhere: generatorVersion bumps to 22.
