Remove OpenPipe integration

OpenPipe was acquired by CoreWeave in September 2025. The Python package
hasn't been updated since June 2025 and the repo since 2024. The openpipe
package caps openai<=1.97.1, creating dependency conflicts with other
extras. Remove the dead integration to clean up the codebase.

pyproject.toml

@@ -99,7 +99,6 @@ novita = []
 nvidia = [ "nvidia-riva-client>=2.25.1,<3" ]
 openai = [ "pipecat-ai[websockets-base]" ]
 rnnoise = [ "pyrnnoise~=0.4.1" ]
-openpipe = [ "openpipe>=4.50.0,<6" ]
 openrouter = []
 perplexity = []
 piper = [ "piper-tts>=1.3.0,<2", "requests>=2.32.5,<3" ]