Add PS_AI_Agent_ElevenLabs plugin (initial implementation)

Adds a new UE5.5 plugin integrating the ElevenLabs Conversational AI Agent
via WebSocket. No gRPC or third-party libs required.

Plugin components:
- UElevenLabsSettings: API key + Agent ID in Project Settings
- UElevenLabsWebSocketProxy: full WS session lifecycle, JSON message handling,
  ping/pong keepalive, Base64 PCM audio send/receive
- UElevenLabsConversationalAgentComponent: ActorComponent for NPC voice
  conversation, orchestrates mic capture -> WS -> procedural audio playback
- UElevenLabsMicrophoneCaptureComponent: wraps Audio::FAudioCapture,
  resamples to 16kHz mono, dispatches on game thread

Also adds .claude/ memory files (project context, plugin notes, patterns)
so Claude Code can restore full context on any machine after a git pull.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/project_context.md

@@ -0,0 +1,79 @@
+# Project Context & Original Ask
+
+## What the user wants to build
+
+A **UE5 plugin** that integrates the **ElevenLabs Conversational AI Agent** API into Unreal Engine 5.5,
+allowing an in-game NPC (or any Actor) to hold a real-time voice conversation with a player.
+
+### The original request (paraphrased)
+> "I want to create a plugin to use ElevenLabs Conversational Agent in Unreal Engine 5.5.
+> I previously used the Convai plugin which does what I want, but I prefer ElevenLabs quality.
+> The goal is to create a plugin in the existing Unreal Project to make a first step for integration.
+> Convai AI plugin may be too big in terms of functionality for the new project, but it is the final goal.
+> You can use the Convai source code to find the right way to make the ElevenLabs version —
+> it should be very similar."
+
+### Plugin name
+`PS_AI_Agent_ElevenLabs`
+
+---
+
+## User's mental model / intent
+
+1. **Short-term**: A working first-step plugin — minimal but functional — that can:
+   - Connect to ElevenLabs Conversational AI via WebSocket
+   - Capture microphone audio from the player
+   - Stream it to ElevenLabs in real time
+   - Play back the agent's voice response
+   - Surface key events (transcript, agent text, speaking state) to Blueprint
+
+2. **Long-term**: Match the full feature set of Convai — character IDs, session memory,
+   actions/environment context, lip-sync, etc. — but powered by ElevenLabs instead.
+
+3. **Key preference**: Simpler than Convai. No gRPC, no protobuf, no ThirdParty precompiled
+   libraries. ElevenLabs' Conversational AI API uses plain WebSocket + JSON, which maps
+   naturally to UE's built-in `WebSockets` module.
+
+---
+
+## How we used Convai as a reference
+
+We studied the Convai plugin source (`ConvAI/Convai/`) to understand:
+- **Module structure**: `UConvaiSettings` + `IModuleInterface` + `ISettingsModule` registration
+- **Audio capture pattern**: `Audio::FAudioCapture`, ring buffers, thread-safe dispatch to game thread
+- **Audio playback pattern**: `USoundWaveProcedural` fed from a queue
+- **Component architecture**: `UConvaiChatbotComponent` (NPC side) + `UConvaiPlayerComponent` (player side)
+- **HTTP proxy pattern**: `UConvaiAPIBaseProxy` base class for async REST calls
+- **Voice type enum**: Convai already had `EVoiceType::ElevenLabsVoices` — confirming ElevenLabs
+  is a natural fit
+
+We then replaced gRPC/protobuf with **WebSocket + JSON** to match the ElevenLabs API, and
+simplified the architecture to the minimum needed for a first working version.
+
+---
+
+## What was built (Session 1 — 2026-02-19)
+
+All source files created and registered. See `.claude/elevenlabs_plugin.md` for full file map and protocol details.
+
+### Components created
+| Class | Role |
+|---|---|
+| `UElevenLabsSettings` | Project Settings UI — API key, Agent ID, security options |
+| `UElevenLabsWebSocketProxy` | Manages one WS session: connect, send audio, handle all server message types |
+| `UElevenLabsConversationalAgentComponent` | ActorComponent to attach to any NPC — orchestrates mic + WS + playback |
+| `UElevenLabsMicrophoneCaptureComponent` | Wraps `Audio::FAudioCapture`, resamples to 16 kHz mono |
+
+### Not yet done (next sessions)
+- Compile & test in UE 5.5 Editor
+- Verify `USoundWaveProcedural::OnSoundWaveProceduralUnderflow` delegate signature for UE 5.5
+- Add lip-sync support (future)
+- Add session memory / conversation history (future)
+- Add environment/action context support (future, matching Convai's full feature set)
+
+---
+
+## Notes on the ElevenLabs API
+- Docs: https://elevenlabs.io/docs/conversational-ai
+- Create agents at: https://elevenlabs.io/app/conversational-ai
+- API keys at: https://elevenlabs.io (dashboard)