Function decompose_ci 

pub fn decompose_ci(
    caixa: &Caixa,
    ci: &CiRun,
) -> Result<CanteiroDag, CiDecomposeFailure>

Predicate: decompose a borrowed canteiro_types::CiRun into its typed canteiro_types::CanteiroDag via canteiro_types::decompose, wrapping any canteiro_types::DecomposeError in a typed CiDecomposeFailure view (carrying Caixa::nome) on rejection. The canonical entry-point every per-Acao consumer wraps in its own thiserror Error variant via #[from] — the call site becomes a single let cd = caixa_core::decompose_ci(caixa, ci)?; in place of the prior inline let cd = canteiro_types::decompose(ci).map_err(|source| CiDecomposeFailure { nome: caixa.nome().to_string(), source })?; block.

Takes the borrowed canteiro_types::CiRun as a separate argument (rather than re-borrowing it through require_ci internally) so the axis stays single-purpose — the sibling require_ci presence gate returns the borrowed slot, this predicate consumes it, and the two together form the substrate-canonical two-line per-Acao prelude let ci = caixa_core::require_ci(caixa)?; let cd = caixa_core::decompose_ci(caixa, ci)?; every present + roadmapped per-Acao consumer runs at its entry-point (matching how the sibling per-Servico entry-gate axes keep require_kind and require_single_servico as separate primitives, then compose them into the V0-shape require_v0_servico_shape helper — the compound require + decompose helper is a peer-lift for a later commit when a second per-Acao consumer arrives). The caixa: &Caixa argument is what makes the diagnostic name the offending caixa.lisp — the borrowed Caixa::nome accessor projects through the typed-view constructor unchanged, matching the peer require_ci / require_kind / require_single_servico typed-view constructors.

Lifted to a single helper so the canteiro_types::decompose axis — the same axis every per-Acao consumer runs on its declared :ci slot — lives in exactly one place across every future per-Acao consumer: a future sui-supercacheci::canteiro::emit_gha workflow renderer (the deferred caixa-actions next step named in its own crate docs), a future per-Acao CR materializer’s admission webhook, a future feira lint sub-diagnostic that offers a :deps-repair suggestion on the [canteiro_types::DecomposeError::MissingDependency] arm but not the canteiro_types::DecomposeError::Cycle arm — every consumer reaches for the same one-liner + #[from] and gets the diagnostic-naming-the-offending-caixa contract for free.

Same trajectory as require_kind / KindMismatch on the peer per-renderer kind-gate axis, require_single_servico / ServicoCountMismatch on the peer per-Servico V0-count-gate axis, and require_ci / MissingCiSlot on the peer per-Acao presence-gate axis: one caixa_core::require_*/decompose_ci helper per typed axis, so the diagnostic shape (named caixa, named field) is uniform across the substrate, and every consumer’s Error::From<*> #[from] arm gets the diagnostic-naming-the- offending-caixa contract for free.

Errors

Returns CiDecomposeFailure when canteiro_types::decompose refuses the borrowed :ci run — every failure mode the sibling canteiro_types::DecomposeError enumerates (a duplicate node name, a dependency on an undeclared node, a dependency cycle) lands on this arm. The error carries the caixa’s :nome + the underlying canteiro_types::DecomposeError verbatim so the diagnostic names the offending caixa.lisp and a consumer that fans on the specific arm reaches for err.source directly rather than re-parsing the Display bytes — same shape every consumer’s Error::From<CiDecomposeFailure> converts into the consumer’s local error type.