## What changed
- Add `McpEventStreamManager` to own event stream workers by thread and subscription.
- Wait for activation before completing a start, tag updates with a stream attempt ID, and keep active streams alive independently of their originating runtime.
- Support cancellation and shutdown without depending on output queue capacity, and close streams when MCP access changes or an event server is removed.
- Reconnect reloaded threads to surviving streams so server removal still cancels them.
## Testing
Add coverage for activation, replacement attempts, task reloads, cancellation before activation, full output queues, access changes, and shutdown.
GitOrigin-RevId: b7156bbe62f9375b2138eb62868f052124e2a884
