design: decide whether packs can define [[service]] declarations

[donbox]

Context

During the spec reconciliation pass, [[service]] was confirmed as city.toml-only for 0.13.6. But the question of whether packs should be able to define services is unresolved.

The import and registry packs are effectively services. If a pack provides an HTTP service (workflow handler, proxy, tool server), that's portable definition — it should travel with the pack.

Question

Should [[service]] be legal in pack.toml (portable definition, composed via imports) in addition to city.toml (deployment)?

Considerations

• If yes: pack-defined services compose through imports like agents and commands. City can override or disable.
• If no: services remain deployment-only. Packs that want to provide service behavior do it through commands or external mechanisms.
• MCP server definitions (already in the agent-v2 spec) overlap here — an MCP server is conceptually a service.

Decision

Deferred to post-0.13.6.