Fix tone partition index and update the (AUD-6237)

[hekdh]

Description

Change the index check to include the case where index == total_num. Update find_num array size to DEFAULT_TONE_NUM for longer tone index.

Related

#1391

Testing

Tested on ESP32-S3-Korvo-2 development board using pipline_flash_tone example. When index == total_num, the error was handled properly.

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Checklist

Before submitting a Pull Request, please ensure the following:

• 🚨 This PR does not introduce breaking changes.
• All CI checks (GH Actions) pass.
• Documentation is updated as needed.
• Tests are updated or added as necessary.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.

[CLAassistant]

All committers have signed the CLA.