Host wiring and builder

The composition layer that wraps a taktora_executor::Executor. This cluster :satisfies: Connector framework (FEAT_0030).

Feature: Host wiring and builder FEAT_0037
status: open
satisfies: FEAT_0030
is satisfied by: REQ_0270, REQ_0271, REQ_0272, REQ_0273

The composition layer that wraps a taktora_executor::Executor and registers each connector’s contributed ExecutableItem instances — matching taktora-executor’s existing builder idiom.
Requirement: ConnectorHost builder API REQ_0270
status: approved
satisfies: FEAT_0037
is refined by: IMPL_0040, ADR_0006
is implemented by: BB_0005

taktora-connector-host shall expose ConnectorHost::builder()...with(connector)...build() returning a ConnectorHost that owns a taktora_executor::Executor.
Requirement: ConnectorGateway builder API REQ_0271
status: approved
satisfies: FEAT_0037
is refined by: IMPL_0040
is implemented by: BB_0005

taktora-connector-host shall expose a parallel ConnectorGateway::builder() for the gateway-side composition, producing a binary that owns its own taktora_executor::Executor.
Requirement: Host registers connector items with the executor REQ_0272
status: approved
satisfies: FEAT_0037
is refined by: IMPL_0040
is implemented by: BB_0005

ConnectorHost::build() shall call Executor::add for every ExecutableItem contributed by registered connectors and shall return an executor ready to run.
Requirement: Optional Observer adapter for tracing REQ_0273
status: open
satisfies: FEAT_0037
is refined by: ARCH_0032, IMPL_0040

Behind a default-off tracing cargo feature, the host shall provide an Observer adapter (using taktora-executor-tracing) that forwards HealthEvent and ExecutionMonitor callbacks through the global tracing subscriber.