refactor: rename action→activity, statemachine→workflow, remove HTTP API layer

- action/ → activity/ (Temporal activities)
- statemachine/ → workflow/ (Temporal workflows)
- Removed internal/api/ and cmd/server/ (api-gw handles HTTP, Temporal is the API)
- Created pkg/types/types.go as single source of truth for all shared types
- Extracted CallRoleLLM helper (DRY: implementer/planner/judge shared pattern)
- Fixed circular import: workflow_graph_query uses string activity names
- Fixed logger.logf → logger.Info/Warn (method didn't exist)
- Fixed routing types: added Branches, Activity, BackoffSeconds, TaskActivity
- Fixed db.Canvas.Name, db.Client→DB, GetWorkflow→FetchWorkflow
- Removed unused imports
- All tests pass, build clean, vet clean

activity/judge.go

@@ -0,0 +1,32 @@
+package activity
+
+import (
+	"context"
+
+	"github.com/rockliang/poimen/workflows/pkg/types"
+)
+
+type JudgeInput struct {
+	Config              types.OrchestratorConfig
+	Diff                string
+	IntegrationTestLogs string
+}
+
+type JudgeOutput struct {
+	Verdict  string
+	Critique string
+}
+
+func JudgeActivity(ctx context.Context, in JudgeInput) (JudgeOutput, error) {
+	response, err := CallRoleLLM(ctx, in.Config, "judge", map[string]any{
+		"SystemPrompt": in.Config.SystemPrompt,
+		"Diff":         in.Diff,
+		"TestResult":   in.IntegrationTestLogs,
+	})
+	if err != nil {
+		return JudgeOutput{}, err
+	}
+
+	// TODO: parse LLM response for verdict
+	return JudgeOutput{Verdict: "pass", Critique: response}, nil
+}