feat: Auto-enable override_model_segment_size for short audio in MDXC separator

[Politrees]

Description

This PR introduces automatic detection and handling of short audio files (< 10 seconds) in the MDXC separator to prevent potential issues (as here: #189).

The separator now automatically:

• Detects when input audio is shorter than 10 seconds
• Enables override_model_segment_size parameter automatically if not already set by user
• Logs appropriate warnings to inform the user about the automatic adjustment

Example Log Output

2025-09-22 17:41:42,527 - WARNING - mdxc_separator - Audio duration (3.72s) is less than 10 seconds.
2025-09-22 17:41:42,527 - WARNING - mdxc_separator - Automatically enabling override_model_segment_size for better processing of short audio.

---

• Tested with audio files < 10 seconds
• Tested with audio files > 10 seconds
• Verified warning messages appear correctly