Change transport to new Streamable HTTP

MCP deprecated SSE transport. When the new StreamableHTTP transport lands in MCP's Java SDK we need to switch.

- https://github.com/modelcontextprotocol/java-sdk/commit/2f944349cc77009d020ebddc8b9967b8e1b14baf
- https://github.com/modelcontextprotocol/java-sdk/issues/72#issue-2948080857
- https://github.com/modelcontextprotocol/java-sdk/pull/337