feat: implement client-initiated real-time human input event streams

- Add HumanInputRequiredEvent and HumanInputCompletedEvent to task_events.py
- Implement HTTP server with WebSocket, SSE, and long-polling endpoints
- Add EventStreamManager for connection and event management
- Integrate event emission in agent executor human input flow
- Add comprehensive tests for server endpoints and event integration
- Add optional FastAPI dependencies for server functionality
- Include documentation and example usage
- Maintain backward compatibility with existing human input flow

Addresses issue #3259 for WebSocket/SSE/long-polling human input events

Co-Authored-By: João <joao@crewai.com>

pyproject.toml

@@ -69,6 +69,11 @@ docling = [
 aisuite = [
     "aisuite>=0.1.10",
 ]
+server = [
+    "fastapi>=0.104.0",
+    "uvicorn>=0.24.0",
+    "websockets>=12.0",
+]
 
 [tool.uv]
 dev-dependencies = [
@@ -86,6 +91,10 @@ dev-dependencies = [
     "pytest-timeout>=2.3.1",
     "pytest-xdist>=3.6.1",
     "pytest-split>=0.9.0",
+    "fastapi>=0.104.0",
+    "uvicorn>=0.24.0",
+    "websockets>=12.0",
+    "httpx>=0.25.0",
 ]
 
 [project.scripts]