Fix docs build: mock sounddevice for environments without PortAudio

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/conf.py

@@ -1,8 +1,12 @@
 import os
 import sys
+from unittest.mock import MagicMock
 
 sys.path.insert(0, os.path.abspath(".."))
 
+# Mock sounddevice so Sphinx can import pytheory.play without PortAudio
+sys.modules["sounddevice"] = MagicMock()
+
 project = "PyTheory"
 copyright = "2024, Kenneth Reitz"
 author = "Kenneth Reitz"