Corrupted video (and audio) outputs

Device: M3 Ultra (256GB)
OS: macOS Sequoia 15.7.1

Some combinations of cmd arguments produce corrupted outputs. Not sure which combinations, but it's certainly related to output duration (frame count)

Here's an example frame from the video:

And cmd that generated it:
```
% ./h3 --model ~/models/MiniMax-H3 -p "" -o outputs/releasenotes11.mp4 --seconds 3 --steps 20
tokenizer 1/1
text encoder 50/50
refine text 1/1
precompute AdaLN 50/50
load transformer core 50/50
denoise 20/20
audio VAE 7/7
video VAE load 36/36
FFmpeg 73/73
h3: wrote outputs/releasenotes11.mp4
```

same cmd with shorter output duration (--seconds 2) works well. Might be related to https://github.com/antirez/h3.c/issues/15 not sure.

ffmpeg version (if relevant):
```
ffmpeg version 8.1.2 Copyright (c) 2000-2026 the FFmpeg developers
built with Apple clang version 17.0.0 (clang-1700.6.4.2)
configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/8.1.2_1 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gpl --enable-libsvtav1 --enable-libopus --enable-libx264 --enable-libmp3lame --enable-libdav1d --enable-libvmaf --enable-libvpx --enable-libx265 --enable-openssl --enable-videotoolbox --enable-audiotoolbox --enable-neon
libavutil 60. 26.102 / 60. 26.102
libavcodec 62. 28.102 / 62. 28.102
libavformat 62. 12.102 / 62. 12.102
libavdevice 62. 3.102 / 62. 3.102
libavfilter 11. 14.102 / 11. 14.102
libswscale 9. 5.102 / 9. 5.102
libswresample 6. 3.102 / 6. 3.102
```

full video:

https://github.com/user-attachments/assets/4f65377f-b79e-4c97-9856-5e5980864c8e