Allow OpenAPI x-cli-config to declare the default command layout

[saltbo]

Problem

An API with stable OpenAPI tags cannot declare that Restish should initially generate tag-grouped commands. Users must configure command_layout: tags locally after connecting.

Proposed behavior

Support an API-level field in x-cli-config:

x-cli-config:
  command_layout: tags

• accept flat and tags
• validate remote values with the existing command-layout validator
• apply the value during api connect
• preserve explicit local configuration on reconnect
• reapply the contract default only when replacement is requested
• do not overwrite local layout during api sync
• keep the setting API-level because command registration is API-level

Acceptance criteria

• JSON and YAML documents parse the field
• connecting persists a valid contract default
• generated help uses the selected layout immediately
• invalid values fail with a focused validation error
• reconnect, replace, sync, and local-override precedence are covered
• documents without the field retain existing behavior