zlib decompression wrapper (RFC 1950) #65

Implement a zlib decompression wrapper in the image crate per RFC 1950.

Requirements#

• Parse zlib header: CMF byte (compression method + window size) and FLG byte (check bits, dict flag, compression level)
• Validate the header checksum (CMF*256 + FLG must be multiple of 31)
• Delegate to DEFLATE decompressor for the compressed data
• Verify Adler-32 checksum of the uncompressed data
• API: fn zlib_decompress(input: &[u8]) -> Result<Vec<u8>, ZlibError>

Acceptance Criteria#

• Correctly decompresses zlib-wrapped data
• Rejects invalid headers and checksum mismatches
• Unit tests with known zlib compressed data
• No external dependencies, no unsafe

Dependencies#

• Requires DEFLATE decompressor

Phase 7 — Image Decoders