Add execution control request contracts

internal/domain/domain.go

@@ -1,6 +1,7 @@
 package domain
 
 import (
+	"context"
 	"time"
 )
 
@@ -60,6 +61,9 @@ type CacheControl struct {
 
 // RunRequest represents a request to generate a single artifact.
 type RunRequest struct {
+	OperationTimeout time.Duration
+	// OnPrepared receives borrowed, read-only internal state.
+	OnPrepared       func(context.Context, *PreparedRun)
 	CaptureExchange  bool
 	ContinueFrom     *Exchange
 	PromptID         string

internal/usecase/runner.go

@@ -39,6 +39,7 @@ var (
 	ErrPromptRender     = errors.New("failed to render prompt")
 	ErrLLMGenerate      = errors.New("failed to generate output")
 	ErrValidation       = errors.New("failed to validate output")
+	ErrOperationTimeout = errors.New("operation timeout exceeded")
 )
 
 // Runner executes the Promptkit core use case.