fix(tts): normalize Chinese punctuation before synthesis

[Ben Younes (ousamabenyounes)]

Normalize full-width Chinese punctuation to the ASCII punctuation recommended by the model before tokenization, avoiding a documented source of unstable Chinese speech synthesis.

Test verification (RED → GREEN)

With the fix reverted, the new test fails (RED):

test_normalizes_chinese_punctuation_for_synthesis (test_text_normalization.TextNormalizationTest.test_normalizes_chinese_punctuation_for_synthesis) ... FAIL

======================================================================
FAIL: test_normalizes_chinese_punctuation_for_synthesis (test_text_normalization.TextNormalizationTest.test_normalizes_chinese_punctuation_for_synthesis)
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Traceback (most recent call last):
  File "/home/ousama/contribute-work/microsoft__VibeVoice/tests/test_text_normalization.py", line 78, in test_normalizes_chinese_punctuation_for_synthesis
    self.assertEqual(
AssertionError: Lists differ: [(0, ' 你好，世界。她问：“今天好吗？”我说：‘很好！’')] != [(0, ' 你好,世界.她问:"今天好吗?"我说:\'很好!\'')]

First differing element 0:
(0, ' 你好，世界。她问：“今天好吗？”我说：‘很好！’')
(0, ' 你好,世界.她问:"今天好吗?"我说:\'很好!\'')

- [(0, ' 你好，世界。她问：“今天好吗？”我说：‘很好！’')]
+ [(0, ' 你好,世界.她问:"今天好吗?"我说:\'很好!\'')]

----------------------------------------------------------------------
Ran 1 test in 0.011s

FAILED (failures=1)

With the fix applied, the test passes (GREEN):

test_normalizes_chinese_punctuation_for_synthesis (test_text_normalization.TextNormalizationTest.test_normalizes_chinese_punctuation_for_synthesis) ... ok

----------------------------------------------------------------------
Ran 1 test in 0.002s

OK

Full local suite

Command: python3 -m unittest discover -s tests -v && python3 -m compileall -q vibevoice demo finetuning-asr vllm_plugin

test_normalizes_chinese_punctuation_for_synthesis (test_text_normalization.TextNormalizationTest.test_normalizes_chinese_punctuation_for_synthesis) ... ok

----------------------------------------------------------------------
Ran 1 test in 0.011s

OK

Fix #425