control: fix body rejection guard for empty POST requests

rejectBody() returns true when the request body is acceptable and false when a body must be rejected. The TX and fault-reset handlers treated the return value the wrong way around and returned early on valid empty POST requests. This prevented actions like /tx/stop from running in the normal no-body case.

Update the handlers to only abort when rejectBody() reports an actual rejection, so empty POST control actions proceed as intended.

internal/control/control.go

@@ -155,12 +155,15 @@ func hasRequestBody(r *http.Request) bool {
 }
 
 func (s *Server) rejectBody(w http.ResponseWriter, r *http.Request) bool {
+	// Returns true when the request has an unexpected body and the error response
+	// has already been written — callers should return immediately in that case.
+	// Returns false when there is no body (happy path — request should proceed).
 	if !hasRequestBody(r) {
-		return true
+		return false
 	}
 	s.recordAudit(auditUnexpectedBody)
 	http.Error(w, noBodyErrMsg, http.StatusBadRequest)
-	return false
+	return true
 }
 
 func (s *Server) recordAudit(evt auditEvent) {