feat(tui): workflow-start intent input box wired to StartSession.input

apps/tui-go/internal/app/view.go

@@ -208,6 +208,8 @@ func (m Model) renderInput() string {
 
 	placeholder := "Ask anything…"
 	switch {
+	case m.inputMode == ModeIntent:
+		placeholder = "Describe the task for " + m.wfPendingName + " (Enter to start, empty = none)…"
 	case m.inputMode == ModeFilter:
 		placeholder = "Filter sessions…"
 	case m.displayState() == StateIdle:
@@ -241,6 +243,9 @@ func (m Model) renderInput() string {
 	if m.inputMode == ModeFilter {
 		mode = "filter"
 	}
+	if m.inputMode == ModeIntent {
+		mode = "task"
+	}
 	sub := lipgloss.NewStyle().Foreground(t.P.Accent2).Background(t.P.Bg).Render(name)
 	if m.selectedID != "" {
 		sub += t.span(" · ", t.P.Faint) +