feat: update access token environment variables and enhance device signing process for E2EE agents; add verification script and system flow documentation

agents/runtime.go

@@ -68,6 +68,13 @@ func New(cfg *config.AgentConfig, rules []decision.Rule, logger *slog.Logger) (*
 			}
 		}
 
+		// Sign own device with the self-signing key so Element shows it as verified.
+		if err := matrixClient.SignOwnDevice(context.Background()); err != nil {
+			logger.Warn("failed to sign own device (non-fatal)", "err", err)
+		} else {
+			logger.Info("own device signed with cross-signing key")
+		}
+
 		logger.Info("e2ee ready")
 	}