APNG IDAT/fdAT Chunk, Streaming Deflate Replay and Disposal Method Frame-Timing Analyzer

Implements the Mozilla community APNG specification on top of the ISO PNG chunk model: acTL must precede the first IDAT and its numframes must equal the fcTL count (0 is invalid); the default image joins the animation only when its fcTL precedes the first IDAT and then must cover the full canvas at (0,0); fcTL and fdAT share one sequence space that must run 0,1,2,… without gaps or duplicates, and out-of-order chunks are errors; delayden = 0 is normalized to 100 (hundredths of a second) while delaynum = 0 means render the next frame as fast as possible. Each frame's compressed stream is the concatenation of its IDAT (or fdAT minus the 4-byte sequence number) chunks; after inflation it must measure exactly height × (1 + ceil(width × bitsPerPixel / 8)) with the filter byte per scanline, so truncated or corrupt zlib streams are caught precisely. The disposal replay flags disposeop = PREVIOUS on the first frame (spec-required downgrade to BACKGROUND), counts zero-delay frames and reports whether any frame actually needs the previous-buffer copy. Pure TypeScript with node:zlib — files are analyzed locally in bounded memory.