Summary

• Handle Azure STT recognizer cancellation and session lifecycle events so cancellations are surfaced through pipeline errors instead of failing silently.
• Add cancellation tracing attributes (reason, code, recoverable, phase, and region) for improved observability of Azure STT failures.
• Guard the STT audio path to stop accepting audio once recognition is terminated and wait for recognizer startup completion.
• Add focused unit tests for startup handler wiring, canceled event error propagation, cancellation default handling, and post-termination audio dropping.
• Include changelog fragments for both behavior changes and bug fixes (changelog/4017.changed.md, changelog/4017.fixed.md).

Testing

• uv run pytest tests/test_azure_stt.py
• uv run ruff check src/pipecat/services/azure/stt.py src/pipecat/utils/tracing/service_decorators.py tests/test_azure_stt.py