feat: Add WebSocket RCON client to companion agent

Wire gorilla/websocket into the Go companion agent to send arbitrary
console commands (e.g. oxide.reload BetterLoot) to the Rust Dedicated
Server's WebRCON endpoint. Adds RCON_PORT and RCON_PASSWORD env vars,
a new "command" action on the existing cmd.server NATS subject, and
the internal/rcon package that handles the JSON-over-WebSocket protocol.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

companion-agent/internal/app/daemon.go

@@ -13,6 +13,7 @@ import (
 	"github.com/vigilcyber/corrosion-companion/internal/filemanager"
 	"github.com/vigilcyber/corrosion-companion/internal/files"
 	"github.com/vigilcyber/corrosion-companion/internal/process"
+	"github.com/vigilcyber/corrosion-companion/internal/rcon"
 	"github.com/vigilcyber/corrosion-companion/internal/update"
 )
 
@@ -25,6 +26,8 @@ type DaemonConfig struct {
 	GameServerArgs    string
 	Version           string
 	InstallDir        string
+	RconPort          int
+	RconPassword      string
 }
 
 // Daemon manages the companion agent's main operations
@@ -155,7 +158,8 @@ func (d *Daemon) subscribeServerCommands() error {
 
 	sub, err := d.nc.Subscribe(subject, func(msg *nats.Msg) {
 		var cmd struct {
-			Action string `json:"action"`
+			Action  string `json:"action"`
+			Command string `json:"command"`
 		}
 
 		if err := json.Unmarshal(msg.Data, &cmd); err != nil {
@@ -174,6 +178,24 @@ func (d *Daemon) subscribeServerCommands() error {
 			err = d.gameServer.Stop()
 		case "restart":
 			err = d.gameServer.Restart()
+		case "command":
+			if cmd.Command == "" {
+				d.respondError(msg, "invalid_command", "command field is required")
+				return
+			}
+			result, rconErr := rcon.SendCommand(d.cfg.RconPort, d.cfg.RconPassword, cmd.Command)
+			if rconErr != nil {
+				log.Printf("RCON command failed: %v", rconErr)
+				d.respondError(msg, "rcon_failed", rconErr.Error())
+			} else {
+				d.respondSuccess(msg, map[string]interface{}{
+					"action":   "command",
+					"command":  cmd.Command,
+					"response": result,
+					"status":   "success",
+				})
+			}
+			return
 		default:
 			err = fmt.Errorf("unknown action: %s", cmd.Action)
 		}