Harden worker federation and operator UI

internal/domain/domain.go

@@ -66,6 +66,13 @@ type Task struct {
 	Version     int    `json:"version"`
 	Title       string `json:"title,omitempty"`
 	Description string `json:"description,omitempty"`
+	// Block evidence is projected from TaskBlocked so terminal records remain
+	// diagnosable after the live coordinator mapping is gone.
+	Blocker     string    `json:"blocker,omitempty"`
+	BlockedAt   time.Time `json:"blocked_at,omitempty"`
+	LastPaneID  string    `json:"last_pane_id,omitempty"`
+	LastHarness string    `json:"last_harness_id,omitempty"`
+	PaneState   string    `json:"pane_state,omitempty"` // open, closed, unreachable, unknown
 }
 
 type Event struct {
@@ -189,6 +196,9 @@ func ValidatePayload(typ string, p map[string]any) error {
 				return err
 			}
 		}
+		if v, ok := p["pane_state"]; ok && v != "open" && v != "closed" && v != "unreachable" && v != "unknown" {
+			return fmt.Errorf("%w: pane_state invalid", ErrInvalid)
+		}
 	case "TaskAmended":
 		if len(p) == 0 {
 			return fmt.Errorf("%w: amendment cannot be empty", ErrInvalid)