fix: off-by-one in Kokoro::synthesize voice index causes crash

[yocontra]

(Larger fix that includes this here: #943)

Broke this out in case you don't want the other change. If you merge #943 you can close this one.

Kokoro::synthesize computes voiceID as:

size_t voiceID = std::min(phonemes.size() - 1, noTokens);

voice_ is std::array<std::array<float, kVoiceRefSize>, kMaxInputTokens> — 128 elements with valid indices 0–127.

When noTokens equals context_.inputTokensLimit (which can be kMaxInputTokens = 128), and phonemes.size() - 1 >= 128, voiceID becomes 128 — one past the end of the array. This causes an out-of-bounds access that aborts on the RN_ET_Worker0 thread.

Crash stack trace

Thread 14 Crashed:: RN_ET_Worker0
0   libsystem_kernel.dylib    __pthread_kill + 8
1   libsystem_pthread.dylib   pthread_kill + 264
2   libsystem_c.dylib         abort + 100
3   Phasma.debug.dylib        std::array<std::array<float, 256>, 128>::operator[] + 52 (array:269)
4   Phasma.debug.dylib        Kokoro::synthesize(...) + 232 (Kokoro.cpp:202)
5   Phasma.debug.dylib        Kokoro::generate(...) + 448 (Kokoro.cpp:94)

Fix

Cap voiceID at noTokens - 1 instead of noTokens:

size_t voiceID = std::min(phonemes.size() - 1, noTokens - 1);

This keeps the index within the valid range of voice_.