[Bug] UCIS input not cleared after resolving mnemonic

Describe the Bug

After resolving a unicode mnemonic, successfully or not, the input buffer should be cleared. In the current code the old input is kept in the buffer, potentially leading to incorrect resolution of future inputs.

Ex. enter the mnemonic "alpha", input is now "alpha". If you then enter the mnemonic "beta", input contains "betaa", which is incorrect.

I suggest using memset to zero out the input buffer at the end of ucis_finish.

Am I missing something important?

Keyboard Used

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Link to product page (if applicable)

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Operating System

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qmk doctor Output

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Is AutoHotKey / Karabiner installed

• AutoHotKey (Windows)
• Karabiner (macOS)

Other keyboard-related software installed

No response

Additional Context

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