Document one end-to-end managed-agent migration between providers

Goal

Add the first reproducible portability walkthrough using a real source and target provider.

The walkthrough should show

• exporting or recreating the source agent as agents.yaml;
• reviewing the declaration in Git;
• changing the target provider and model mapping;
• the exact validate and plan output;
• native, emulated, and unsupported differences;
• applying and running one equivalent session on the target;
• cleanup steps and cost/security caveats.

Start by proposing the provider pair in Discussion #8. Do not commit credentials, state files, workspace identifiers, or unredacted provider payloads.

Comece pela Discussion #8 para propor e selecionar o par de provedores. Em seguida, documente a migração usando agents.yaml, incluindo a saída exata de validate e plan, o mapeamento de provedores e modelos, as diferenças de portabilidade, as etapas de apply e session, a limpeza e as ressalvas de custo e segurança. Está concluído quando o passo a passo puder ser reproduzido sem credenciais, arquivos de estado, identificadores do workspace ou payloads de provedores não redigidos.