Add Inworld Realtime Service (#4140)

* Add Inworld Realtime LLM service

Adds a WebSocket-based realtime service for Inworld's cascade
STT/LLM/TTS API with semantic VAD, function calling, and streaming
transcription support.

New files:
- src/pipecat/services/inworld/realtime/ (service, events)
- src/pipecat/adapters/services/inworld_realtime_adapter.py
- examples/foundational/19zb-inworld-realtime.py

Also includes:
- websockets dependency for inworld extra in pyproject.toml
- Adapter and settings tests matching OpenAI/Grok realtime patterns
- Fix for double-response when server-side VAD is enabled

* Prefer init-provided system instruction in Inworld Realtime

Adopt _resolve_system_instruction() from BaseLLMAdapter, matching the
pattern applied to OpenAI Realtime, Grok Realtime, Gemini Live, and
Nova Sonic in the pk/realtime-services-init-v-context-system-instructions-cleanup
branch.

* Update changelog entry with PR number

* Fix changelog format to use bullet point

* Polish PR: default model, example cleanup, changelog update

- Change default model from gpt-4.1-nano to gpt-4.1-mini
- Add function calling demo to example
- Remove demo-testing artifact from system instruction
- Mention Router support in changelog

* Address PR review feedback for Inworld Realtime

- Move example to examples/realtime/realtime-inworld.py
- Change initial context role from "user" to "developer"
- Remove explicit sample rates from example; sync them in
  _ensure_audio_config so Inworld gets the transport's actual rates
- Add audio race condition guard in _handle_evt_audio_delta (matches
  OpenAI realtime pattern)
- Convert remaining "system"/"developer" messages to "user" in adapter
- Add clarifying comment for local-VAD vs server-VAD metrics paths

* Simplify example, add provider tracking, remove local VAD path

- Remove function calling from example, switch model to xai/grok-4-1-fast-non-reasoning
- Add pipecat-realtime session key prefix and provider_data metadata
  for Inworld traffic attribution
- Remove local VAD code path (Inworld only supports server-side VAD)
- Use typed InputAudioBufferAppendEvent for audio sends

* Default TTS model to inworld-tts-1.5-max

* Remove dead shimmed tools code, set STT/VAD defaults

- Remove non-functional AdapterType.SHIM custom tools code from adapter
- Default STT model to assemblyai/u3-rt-pro
- Default VAD eagerness to low

pyproject.toml

@@ -77,7 +77,7 @@ groq = [ "groq>=0.23.0,<2" ]
 gstreamer = [ "pygobject~=3.50.0" ]
 heygen = [ "livekit>=1.0.13,<2", "pipecat-ai[websockets-base]" ]
 hume = [ "hume>=0.11.2,<1" ]
-inworld = []
+inworld = [ "pipecat-ai[websockets-base]" ]
 koala = [ "pvkoala~=2.0.3" ]
 kokoro = [ "kokoro-onnx>=0.5.0,<1", "requests>=2.32.5,<3" ]
 langchain = [ "langchain>=1.2.13,<2", "langchain-community>=0.4.1,<1", "langchain-openai>=1.1.12,<2" ]