[FEATURE] Add Support for Streamable HTTP MCP

**Feature description**
Add support for streaming HTTP responses when using the Amazon Bedrock Client for Mac with Managed Content Processing (MCP).

**Problem it solves**
Currently, the Amazon Bedrock Client for Mac does not support streaming HTTP responses for MCP. This limitation affects users who need real-time responses for better user experience and reduced latency, particularly with longer responses from foundation models.

**Proposed solution**
Implement Server-Sent Events (SSE) processing to handle streaming responses from Amazon Bedrock when using MCP. This would allow the client to display partial responses as they arrive rather than waiting for the complete response.

**Alternatives considered**
- WebSocket implementation: More complex and may be overkill for this use case
- Polling: Less efficient than true streaming

**Additional context**
This feature has been directly requested by Rapid7, an AWS XL ISV customer currently using the tool. Adding streaming support would significantly enhance their experience with the client.

**Environment**
- macOS version: All supported versions
- Amazon Bedrock Client for Mac version: Current version