feat: authenticate Windows command launcher and signal helper

internal/client/supervisor/windows/launcher_wire.go

@@ -0,0 +1,58 @@
+package windows
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// Wire payloads are JSON only inside the authenticated private pipe.  The
+// outer frame still supplies a bounded binary length, generation and digest;
+// JSON keeps the launcher mode stateless and makes malformed-field rejection
+// explicit rather than relying on Go's gob type registry.
+type launcherHello struct {
+	PID       uint32 `json:"pid"`
+	Creation  uint64 `json:"creation"`
+	SessionID uint32 `json:"session_id"`
+	Effective string `json:"effective_sid"`
+}
+
+type launcherRequest struct {
+	ApplicationName  string   `json:"application_name"`
+	CommandLine      string   `json:"command_line"`
+	WorkingDirectory string   `json:"working_directory"`
+	Environment      []uint16 `json:"environment"`
+}
+
+type launcherShellPrepared struct {
+	PID      uint32 `json:"pid"`
+	Creation uint64 `json:"creation"`
+}
+
+type signalHelperRequest struct {
+	PID       uint32 `json:"pid"`
+	Creation  uint64 `json:"creation"`
+	SessionID uint32 `json:"session_id"`
+}
+
+type signalHelperResult struct {
+	Delivered bool   `json:"delivered"`
+	Detail    string `json:"detail"`
+}
+
+func marshalLauncherPayload(value any) ([]byte, error) {
+	payload, err := json.Marshal(value)
+	if err != nil {
+		return nil, err
+	}
+	if len(payload) > launcherMaxFrameBytes {
+		return nil, fmt.Errorf("launcher payload exceeds %d bytes", launcherMaxFrameBytes)
+	}
+	return payload, nil
+}
+
+func unmarshalLauncherPayload(payload []byte, target any) error {
+	if len(payload) == 0 || len(payload) > launcherMaxFrameBytes {
+		return fmt.Errorf("launcher payload length %d is invalid", len(payload))
+	}
+	return json.Unmarshal(payload, target)
+}