Fix _get_feat_extract_output_lengths in qwen3_omni_moe

[hkc5]

This PR fixes the unexpected behaviour of helper function _get_feat_extract_output_lengths in qwen3_omni_moe as reported in #45083.

Problem

The current implementation incorrectly calculates the output length of the convolutional layers by:

1. Taking modulo 100 of input lengths
2. Adding a correction factor of (input_lengths // 100) * 13

This does not align with the official PyTorch Conv2d formula.

Fix

Updated the function to correctly calculate the output length based on the PyTorch Conv2d formula:

• For Conv2d with kernel_size=3, stride=2, padding=1: output = (input - 1) // 2 + 1
• Applied sequentially for the 3 conv layers in the audio encoder

Files Changed

• src/transformers/models/qwen3_omni_moe/modeling_qwen3_omni_moe.py
• src/transformers/models/qwen3_omni_moe/modular_qwen3_omni_moe.py
• src/transformers/models/qwen3_omni_moe/processing_qwen3_omni_moe.py

Fixes #45083

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: qwen3_omni_moe