Processor-generated level textures, version 1

Build processors may return an optional assets.json alongside ordinary files in the existing KPR1 response. This extends the build contract; it changes neither the cartridge wire protocol. Processors without a catalog keep returning opaque resources through processed.Read.

{
  "version": 1,
  "textures": [
    {
      "level": "village",
      "name": "generated-background",
      "source": "generated/background.png",
      "key": "generated/background.png#0,0,1024,1024",
      "profile": "sprite"
    }
  ]
}

level names an existing directory under the project's levels/. source names a PNG in the same response; it is a logical path, never a filesystem write destination. key is the processor's lookup identity. Names must be unique within a level, and keys unique within a processor. Paths cannot escape, contain NUL, use backslashes or contain drive prefixes. Unknown catalog fields, invalid PNGs, missing sources and collisions with authored texture names fail the build.

The CLI validates every result before replacing its owned .karty/processed/ transaction. Images live under that ignored directory and pass through the normal texture processing profile and level packager. They are not embedded into generated Go source. The catalog and generated lookup are also ignored build outputs:

id, ok := processed.TextureID("tiled.compile", imageKey)

Authored texture IDs retain their existing name-sorted order. Generated textures follow them in name order. A changed authored catalog requires rebuilding the processor output; stale generated IDs are rejected. Rebuilding creates a complete matching map, lookup and level distribution without editing authored assets.

KPR1 retains its limits of 256 files and 16 MiB of aggregate file content per request or response. The catalog is at most 64 KiB and 256 textures. Generated PNG decoding is bounded to 4096 pixels per edge and 256 MiB of aggregate decoded pixels per processor. Normal asset-pipeline limits apply afterward.

The Tiled processor uses this contract for explicitly selected static background layers. Its original map output retains gameplay data; a separate render map references the generated textures. Dynamic scenery, animation, collisions, quests and original source images remain authored inputs. The build never writes merged PNGs back into levels/.