(workflow) add simple harness workflow for manual testing

action/implementer.go

@@ -1,3 +1,93 @@
 package action
 
-// Empty stub - will be filled in T0.5
+import (
+	"context"
+	"fmt"
+
+	"github.com/rockliang/poimen/workflows/action/llm"
+	"github.com/rockliang/poimen/workflows/prompts"
+	"github.com/rockliang/poimen/workflows/statemachine"
+	"go.temporal.io/sdk/activity"
+)
+
+// ImplementerInput is input to ImplementerActivity.
+type ImplementerInput struct {
+	Config      statemachine.OrchestratorConfig
+	TaskID      string
+	WorktreePath string
+	Lessons     string // "known errors — do not repeat" section
+}
+
+// ImplementerOutput is the output of ImplementerActivity.
+type ImplementerOutput struct {
+	Success bool
+	Changes string // summary of changes made
+}
+
+// ImplementerActivity calls the Implementer LLM to implement the task.
+func ImplementerActivity(ctx context.Context, in ImplementerInput) (ImplementerOutput, error) {
+	// Record heartbeat
+	activity.RecordHeartbeat(ctx, "starting implementer for "+in.TaskID)
+
+	// Get LLM client
+	client, err := llm.NewClient()
+	if err != nil {
+		return ImplementerOutput{}, fmt.Errorf("failed to create LLM client: %w", err)
+	}
+
+	// Get implementer spec
+	implementerSpec, exists := in.Config.RolePrompts["implementer"]
+	if !exists {
+		return ImplementerOutput{}, fmt.Errorf("implementer role prompt not configured")
+	}
+
+	// Build variables for template
+	templateVars := map[string]any{
+		"SystemPrompt": in.Config.SystemPrompt,
+		"Task":         in.TaskID,
+		"WorktreePath": in.WorktreePath,
+	}
+
+	// Inject lessons if provided
+	if in.Lessons != "" {
+		templateVars["Lessons"] = in.Lessons
+	}
+
+	// Render template
+	var templateContent string
+	if implementerSpec.RawTemplate != "" {
+		templateContent = implementerSpec.RawTemplate
+	} else {
+		// Parse and render the embedded template
+		templateContent, err = prompts.Render(implementerSpec.TemplateRef, templateVars)
+		if err != nil {
+			return ImplementerOutput{}, fmt.Errorf("failed to render implementer template: %w", err)
+		}
+	}
+
+	// Call LLM
+	messages := []llm.MessageParam{
+		{
+			Role:    "user",
+			Content: templateContent,
+		},
+	}
+
+	response, err := client.CreateMessage(ctx, llm.MessageInput{
+		Model:        implementerSpec.Model,
+		SystemPrompt: in.Config.SystemPrompt,
+		Messages:     messages,
+	})
+	if err != nil {
+		return ImplementerOutput{}, fmt.Errorf("implementer LLM call failed: %w", err)
+	}
+
+	// Record progress
+	activity.RecordHeartbeat(ctx, "implementer completed for "+in.TaskID)
+
+	// Return success (in full implementation would parse response and execute tool calls)
+	return ImplementerOutput{
+		Success: true,
+		Changes: response,
+	}, nil
+}