Handle JsonRpcError in initialize

[wzxxing]

Describe the bug
A clear and concise description of what the bug is.

When the MCP protocol initialization failed, the server can return a JSON RPC Error object, which is currently ignored by the rust SDK.

rust-sdk/crates/rmcp/src/service/client.rs

Lines 128 to 129 in 94428d5

	// Server SHOULD NOT send any other messages before handshake. We ignore them anyway
	_ => tracing::warn!(?message, "Received unexpected message"),

The Specification suggested that

Implementations SHOULD be prepared to handle these error cases:

https://modelcontextprotocol.io/specification/2025-03-26/basic/lifecycle#error-handling

To Reproduce
Steps to reproduce the behavior:

1. I found this when using the Kiro CLI which uses the rust-sdk. Plugging a MCP server that initialize failure. The error can only be found through tracing

2025-11-26T11:05:21.291608Z  WARN rmcp::service::client: 129: Received unexpected message Error(JsonRpcError { jsonrpc: JsonRpcVersion2_0, id: Number(0), error: ErrorData { code: ErrorCode(-32001), message: "Your AWS session token has expired. Please refresh your credentials and try again. If you're using temporary credentials, you may need to re-authenticate to obtain new credentials.", data: None } })

expect_response ignores the mcp jsonrpc error, hence there was never a response received by the client.

rust-sdk/crates/rmcp/src/service/client.rs

Lines 229 to 235 in 94428d5

	let (response, response_id) = expect_response(
	&mut transport,
	"initialize response",
	&service,
	peer.clone(),
	)
	.await?;

Because my test-mcp server quits after the initialization error, I got a very generic "connection closed" message.

Expected behavior

My test server response to initialization with a synthesized JSON RPC error, I expect the JSON RPC error should be used as the ClientInitializeError.

Logs
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Additional context
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