Amazon Bedrock AgentCore Samples - [Bug] MCP example doesn't surface correct exception

**Describe the bug**
Customer was seeing the issue:

```
bash> python my_mcp_client_remote.py
Using AWS region: us-west-2
Retrieved Agent ARN: arn:aws:bedrock-agentcore:us-west-2::runtime/mcp_server-zzzzzzz
✓ Retrieved bearer token from Secrets Manager

Connecting to: https://bedrock-agentcore.us-west-2.amazonaws.com/runtimes/arn%3Aaws%3Abedrock-agentcore%3Aus-west-2%3A256215987095%3Aruntime%2Fmcp_server-kOjvNZ4q0I/invocations?qualifier=DEFAULT
Headers configured ✓

🔄 Initializing MCP session...
❌ Error connecting to MCP server: unhandled errors in a TaskGroup (1 sub-exception)
```

Underlying issue was:
```
com.amazon.awsrequestauth.exception.UnauthorizedInboundTokenException: Token has expired
at com.amazon.awsrequestauth.validator.BearerTokenValidator.validateTokenTimeboundPayload(BearerTokenValidator.java:156)
```
**Expected behavior**
Can we transparently surface exceptions, atleast enable debug log in our samples

Start with the my_mcp_client_remote.py sample and reproduce the shown connection flow, including the expired-token case. Trace how the MCP initialization error is reported; done means the underlying token exception is surfaced or debug logging is enabled clearly enough to identify it.

Written by the indexing model from the issue text.