pipecat/changelog/3851.removed.md

• ⚠️ Removed ProcessingMetricsData and all start_processing_metrics()/stop_processing_metrics() methods from FrameProcessor and FrameProcessorMetrics. These metrics were inconsistently implemented across services and overlapped with the better-defined TTFB metric. TTFB, LLM token usage, TTS character usage, and text aggregation metrics are unaffected.