fix: correct type-check order in _generate() to prevent AttributeError on non-string input

The previous guard `not text.strip() or not isinstance(text, str)` called
.strip() before verifying that text is actually a string, causing an
AttributeError (e.g. for int input) instead of the intended ValueError.

Swap operand order so isinstance check short-circuits first.

Closes #228

src/voxcpm/core.py

@@ -200,7 +200,7 @@ class VoxCPM:
             Yields audio chunks for each generation step if ``streaming=True``,
             otherwise yields a single array containing the final audio.
         """
-        if not text.strip() or not isinstance(text, str):
+        if not isinstance(text, str) or not text.strip():
             raise ValueError("target text must be a non-empty string")
 
         if prompt_wav_path is not None: