feat(tui-go): interactive clarification question view

Render stage clarification questions as an AskUserQuestion-style form:
header chip, prompt, selectable option chips, and a free-text custom slot.
Arrow/hjkl nav, space to select, e for custom, enter to submit. Submit
guards on all-answered and sends ClarificationResponse; the parked stage
re-runs with the answers in context.

apps/tui-go/internal/protocol/protocol.go

@@ -34,6 +34,7 @@ const (
 	TypeToolRejected     = "tool.rejected"
 	TypeApprovalRequired = "approval.required"
 	TypeApprovalResolved = "approval.resolved"
+	TypeClarification    = "clarification.required"
 	TypeWorkspaceBound   = "session.workspace_bound"
 	TypeStageManifest    = "stage.tool_manifest"
 	TypeProviderStatus   = "provider.status_changed"
@@ -135,6 +136,26 @@ type ServerMessage struct {
 
 	// session.stats — derived metrics for a session (reply to GetSessionStats)
 	Stats *StatsDto `json:"stats"`
+
+	// clarification.required — open questions a stage raised for the operator
+	Questions []ClarificationQuestionDto `json:"questions"`
+}
+
+// ClarificationQuestionDto is one open question from a stage. Empty Options ->
+// free-text answer; non-empty -> selectable choices. Mirrors the Kotlin
+// ClarificationQuestion (core:events), which is the wire shape.
+type ClarificationQuestionDto struct {
+	ID          string   `json:"id"`
+	Prompt      string   `json:"prompt"`
+	Options     []string `json:"options"`
+	MultiSelect bool     `json:"multiSelect"`
+	Header      string   `json:"header"`
+}
+
+// ClarificationAnswerDto is the operator's answer to one question.
+type ClarificationAnswerDto struct {
+	QuestionID string `json:"questionId"`
+	Value      string `json:"value"`
 }
 
 // StatsDto mirrors the server's MetricsReport: a session's derived metrics
@@ -291,7 +312,8 @@ func (m ServerMessage) IsEventBearing() bool {
 		TypeInferenceFailed, TypeInferenceRetry,
 		TypeToolStarted, TypeToolCompleted, TypeToolFailed, TypeToolRejected,
 		TypeToolAssessed,
-		TypeApprovalRequired, TypeApprovalResolved, TypeWorkspaceBound, TypeArtifactCreated,
+		TypeApprovalRequired, TypeApprovalResolved, TypeClarification,
+		TypeWorkspaceBound, TypeArtifactCreated,
 		TypeArtifactValid, TypePlanLocked,
 		TypeRouterNarration:
 		return true
@@ -362,6 +384,17 @@ func ApprovalResponse(requestID, decision string, steeringNote *string) []byte {
 	})
 }
 
+// ClarificationResponse answers a stage's open questions; the parked stage re-runs
+// with the answers in context.
+func ClarificationResponse(sessionID, stageID, requestID string, answers []ClarificationAnswerDto) []byte {
+	return encode("ClarificationResponse", map[string]any{
+		"sessionId": sessionID,
+		"stageId":   stageID,
+		"requestId": requestID,
+		"answers":   answers,
+	})
+}
+
 // Ping is a keepalive.
 func Ping(ts int64) []byte {
 	return encode("Ping", map[string]any{"timestamp": ts})