bug: mcpServers schema requires "command" even for HTTP-based MCP servers

### 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

WSL

### Expected behaviour

In the agent-v1.json schema, each entry under mcpServers requires the "command" field.
This requirement does not make sense for MCP servers that use "type": "http", since HTTP servers connect via a URL instead of a local command.

https://github.com/aws/amazon-q-developer-cli/blob/main/schemas/agent-v1.json

### Actual behaviour

### Steps to reproduce

* Define an MCP server with "type": "http" and "url": "https://knowledge-mcp.global.api.aws".
* Validate it against the schema.
* Validation fails because "command" is missing.

### Environment

```yaml

```