Canonical build-time invocation point for the Exeris codegen pipeline. `exeris:generate` runs the kernel-target generators against the processor-emitted DomainMetadata and writes sources into src/main/generated/java (L1). `exeris:detach` promotes that output into src/main/java and stops regeneration (L2 detachment). A thin Maven shell over CodegenPipeline — no emission logic lives here.