nx_png_chunks.nx

nx_png_chunks.nx -- THE PNG CHUNK WALK (one reader, shared): signature, then [length(4, big-endian)][type(4)][data][crc(4)] until IEND. First consumer is companionchat CC2 (a Tavern V2 character card is base64 JSON inside a tEXt chunk whose keyword is `chara`); gen G15 (workflow ingest from a rival's PNG metadata) names the same walk. EXTRACTED here so there is exactly one chunk walker in the estate -- go_png_dim in the orchestrator reads only the IHDR dimensions and stays as is. DECLARED IMPRECISION: CRCs are not verified. This walker EXTRACTS metadata; it does not validate an image, and a wrong CRC on a text chunk cannot change the bytes it returns. A chunk whose declared length overruns the buffer is MALFORMED and the walk stops there rather than reading past the end. license_tier: ORIGINAL