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

```

Beginne damit, die Verbindung zu einem HTTPS MCP-Server nachzustellen, der den Mcp-Session-Id-Antwort-Header weglässt, und verfolge anschließend die HTTP-Initialisierungsbehandlung des MCP-Clients. Erledigt ist die Aufgabe, wenn der Client erfolgreich eine Verbindung herstellt, sobald dieser optionale Header fehlt, und nicht mehr eine fehlende Sitzungs-ID oder eine geschlossene Initialize-Antwort meldet.

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