## Why
MCP requests need to retain inbound W3C trace context even when no OpenTelemetry tracing layer is installed.
## What changed
- Carry validated request trace context through app-server MCP tasks, connection startup, and resource listing tasks, while preferring active span context.
- Forward fallback `traceparent` and `tracestate` headers for MCP HTTP requests, including discovery and initialization.
- Use HTTP trace headers as a fallback for exec-server RPC calls when active span context is unavailable.
## Testing
Add an app-server integration test that disables trace exporting and verifies that `mcpServer/resource/read` forwards the inbound `traceparent` and `tracestate` to the MCP server.
GitOrigin-RevId: c886a55ce0a3992f1b2e04614efec80a20cb4b49
Joe Savona
3cd64c8d7c