bug: MCP client expects session id from server when spec says it is optional.

### Checks

- [x] I have searched [github.com/aws/amazon-q-developer-cli/issues](https://github.com/aws/amazon-q-developer-cli/issues?q=) and there are no duplicates of my issue
- [x] I have run `q doctor` in the affected terminal session
- [x] I have run `q restart` and replicated the issue again

### Operating system

MacOS

### Expected behaviour

Connecting to an HTTP MCP server should work regardless of the implementation of a header session id.

https://modelcontextprotocol.io/specification/2025-06-18/basic/transports#session-management

### Actual behaviour

Amazon Q cannot connect to MCP servers that do not offer a session id in their response headers.

### Steps to reproduce

Create an HTTPS transport MCP server that does not create or return a header of Mcp-Session-Id to the MCP client. Try to connect to this MCP server, it will fail with a message like
`worker quit with fatal: Missing session id in HTTP response, when process initialize response`
and
`McpError(ErrorData { code: ErrorCode(-32002), message: "connection closed: initialize response", data: None })`

### Environment

```yaml

```

Inizia riproducendo la connessione a un server HTTPS MCP che omette l’header di risposta Mcp-Session-Id, quindi traccia la gestione dell’inizializzazione HTTP del client MCP. Il lavoro è completato quando il client si connette correttamente in assenza di questo header opzionale e non segnala più un ID di sessione mancante o una risposta Initialize chiusa.

Scritto dal modello di indicizzazione a partire dal testo della issue.