CRITICAL: PNG animation frames corrupted - ZLIB inflate error -3 breaks FFmpeg

[krystophny]

DEFECT: Animation PNG frames have corrupted ZLIB compression causing FFmpeg decode failures

REPRODUCTION:

1. Run make example (animation examples)
2. FFmpeg receives PNG frames with corrupt ZLIB data
3. Error: 'inflate returned error -3' (ZLIB decompression failure)
4. All animation frames fail to decode: 'Generic error in an external library'

EVIDENCE:

• Static PNG files work perfectly (validated with file command)
• Animation PNG sequence generation produces corrupt ZLIB streams
• FFmpeg error: '[png] inflate returned error -3' on every frame
• Error: 'Decode error rate 1 exceeds maximum 0.666667'

USER IMPACT: HIGH - All animation functionality broken
ROOT CAUSE: Custom ZLIB implementation corruption in animation PNG sequence
TECHNICAL DETAILS:

• Static PNG: Working ZLIB compression
• Animation PNG: Corrupt ZLIB streams cause inflate() failures
• FFmpeg cannot process any animation frames

SOLUTION: Fix ZLIB compression corruption in animation PNG generation

[krystophny]

Duplicate of #983; consolidating PNG compression/FFmpeg inflate -3 under #983.