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/app/model.go

@@ -12,6 +12,7 @@ const (
 	StateIdle DisplayState = iota
 	StateInSession
 	StateApproval
+	StateClarification
 )
 
 // InputMode toggles what a submitted line targets.
@@ -107,6 +108,23 @@ type Approval struct {
 	Rationale []string
 }
 
+// ClarQuestion is one open question a stage raised (mirrors the wire DTO).
+type ClarQuestion struct {
+	ID          string
+	Prompt      string
+	Header      string
+	Options     []string
+	MultiSelect bool
+}
+
+// Clarification is a stage's pending set of open questions for the operator.
+type Clarification struct {
+	RequestID string
+	SessionID string
+	StageID   string
+	Questions []ClarQuestion
+}
+
 // Session is the UI's view of one server session.
 type Session struct {
 	ID            string
@@ -122,7 +140,8 @@ type Session struct {
 	ToolsByStage  map[string][]ManifestTool
 	Events        []EventEntry
 	Pending       *Approval
-	Active        bool // an inference/tool is in flight (drives the spinner)
+	Clar          *Clarification // open questions awaiting answers (clarification view)
+	Active        bool           // an inference/tool is in flight (drives the spinner)
 }
 
 // Workflow is a launchable workflow advertised by the server.
@@ -229,6 +248,14 @@ type Model struct {
 	// approval steering input buffer
 	steerBuffer string
 	steering    bool
+
+	// clarification view (the interactive question form)
+	clarFocus     int            // focused question index
+	clarCursor    int            // option cursor in the focused question (== len(opts) → custom slot)
+	clarChosen    []map[int]bool // per-question selected option indices
+	clarText      []string       // per-question free-text / custom answer
+	clarTyping    bool           // typing into the custom buffer for the focused question
+	clarDismissed bool           // peeked away from the form (it can be reopened)
 }
 
 // NewModel builds the initial idle state.
@@ -257,10 +284,16 @@ func (m Model) displayState() DisplayState {
 	if m.selectedID == "" || !m.sessionEntered {
 		return StateIdle
 	}
+	s := m.session(m.selectedID)
+	// A stage's open questions take precedence: the run is parked on them, and they
+	// must be answered (or peeked away) before anything else makes sense.
+	if s != nil && s.Clar != nil && !m.clarDismissed {
+		return StateClarification
+	}
 	if m.approvalDismissed {
 		return StateInSession
 	}
-	if s := m.session(m.selectedID); s != nil && s.Pending != nil {
+	if s != nil && s.Pending != nil {
 		return StateApproval
 	}
 	return StateInSession