feat: Add Oxide/uMod installer package + wire into companion agent daemon

New oxide package downloads latest Oxide.Rust release from GitHub,
extracts over the server directory, and restarts the game server.
Progress published to NATS (corrosion.{license_id}.oxide.status).
Heartbeat now reports oxide_installed status.

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

companion-agent/internal/app/daemon.go

@@ -11,6 +11,7 @@ import (
 	"github.com/nats-io/nats.go"
 	"github.com/vigilcyber/corrosion-companion/internal/deploy"
 	"github.com/vigilcyber/corrosion-companion/internal/filemanager"
+	"github.com/vigilcyber/corrosion-companion/internal/oxide"
 	"github.com/vigilcyber/corrosion-companion/internal/files"
 	"github.com/vigilcyber/corrosion-companion/internal/process"
 	"github.com/vigilcyber/corrosion-companion/internal/rcon"
@@ -32,14 +33,15 @@ type DaemonConfig struct {
 
 // Daemon manages the companion agent's main operations
 type Daemon struct {
-	nc            *nats.Conn
-	cfg           *DaemonConfig
-	gameServer    *process.GameServer
-	fileOps       *files.Operations
-	fm            *filemanager.FileManager
-	updater       *update.Updater
-	deployer      *deploy.Deployer
-	subscriptions []*nats.Subscription
+	nc              *nats.Conn
+	cfg             *DaemonConfig
+	gameServer      *process.GameServer
+	fileOps         *files.Operations
+	fm              *filemanager.FileManager
+	updater         *update.Updater
+	deployer        *deploy.Deployer
+	oxideInstaller  *oxide.OxideInstaller
+	subscriptions   []*nats.Subscription
 }
 
 // HeartbeatPayload represents the data sent in heartbeat messages
@@ -56,6 +58,7 @@ type HeartbeatPayload struct {
 	OS              string  `json:"os"`
 	Arch            string  `json:"arch"`
 	ServerInstalled bool    `json:"server_installed"`
+	OxideInstalled  bool    `json:"oxide_installed"`
 }
 
 // gameServerAdapter wraps process.GameServer to satisfy deploy.GameServerStarter
@@ -74,6 +77,15 @@ func (a *gameServerAdapter) UpdatePath(path string) {
 	*a.gs = *process.NewGameServer(path, a.cfg.GameServerArgs)
 }
 
+// restartAdapter wraps process.GameServer to satisfy oxide.GameServerRestarter
+type restartAdapter struct {
+	gs *process.GameServer
+}
+
+func (a *restartAdapter) Restart() error {
+	return a.gs.Restart()
+}
+
 // NewDaemon creates a new daemon instance
 func NewDaemon(nc *nats.Conn, cfg *DaemonConfig) (*Daemon, error) {
 	gameServer := process.NewGameServer(cfg.GameServerPath, cfg.GameServerArgs)
@@ -82,15 +94,18 @@ func NewDaemon(nc *nats.Conn, cfg *DaemonConfig) (*Daemon, error) {
 	updater := update.NewUpdater(cfg.Version)
 	adapter := &gameServerAdapter{gs: gameServer, cfg: cfg}
 	deployer := deploy.NewDeployer(nc, cfg.LicenseID, cfg.InstallDir, adapter)
+	restarter := &restartAdapter{gs: gameServer}
+	oxideInst := oxide.NewOxideInstaller(nc, cfg.LicenseID, cfg.InstallDir, restarter)
 
 	d := &Daemon{
-		nc:         nc,
-		cfg:        cfg,
-		gameServer: gameServer,
-		fileOps:    fileOps,
-		fm:         fm,
-		updater:    updater,
-		deployer:   deployer,
+		nc:             nc,
+		cfg:            cfg,
+		gameServer:     gameServer,
+		fileOps:        fileOps,
+		fm:             fm,
+		updater:        updater,
+		deployer:       deployer,
+		oxideInstaller: oxideInst,
 	}
 
 	return d, nil
@@ -125,6 +140,11 @@ func (d *Daemon) Run(ctx context.Context) error {
 		return fmt.Errorf("failed to subscribe to deploy commands: %w", err)
 	}
 
+	// Subscribe to Oxide install commands
+	if err := d.subscribeOxideInstall(); err != nil {
+		return fmt.Errorf("failed to subscribe to oxide install commands: %w", err)
+	}
+
 	// Subscribe to file manager commands (VueFinder-compatible request-reply)
 	if err := d.subscribeFileManager(); err != nil {
 		return fmt.Errorf("failed to subscribe to file manager commands: %w", err)
@@ -389,6 +409,38 @@ func (d *Daemon) subscribeFileManager() error {
 	return nil
 }
 
+// subscribeOxideInstall subscribes to Oxide installation commands
+func (d *Daemon) subscribeOxideInstall() error {
+	subject := fmt.Sprintf("corrosion.%s.cmd.oxide", d.cfg.LicenseID)
+
+	sub, err := d.nc.Subscribe(subject, func(msg *nats.Msg) {
+		log.Println("Received Oxide install command")
+
+		// Run installation in goroutine (it's long-running)
+		go func() {
+			if err := d.oxideInstaller.Install(); err != nil {
+				log.Printf("Oxide installation failed: %v", err)
+			} else {
+				log.Println("Oxide installation completed successfully")
+			}
+		}()
+
+		// Immediately acknowledge the command
+		d.respondSuccess(msg, map[string]interface{}{
+			"status":  "accepted",
+			"message": "Oxide installation started, progress will be published to oxide.status",
+		})
+	})
+
+	if err != nil {
+		return err
+	}
+
+	d.subscriptions = append(d.subscriptions, sub)
+	log.Printf("Subscribed to: %s", subject)
+	return nil
+}
+
 // handleFileOperation processes file operation requests
 func (d *Daemon) handleFileOperation(msg *nats.Msg) {
 	// Parse common fields
@@ -459,6 +511,7 @@ func (d *Daemon) publishHeartbeat() {
 		OS:              runtime.GOOS,
 		Arch:            runtime.GOARCH,
 		ServerInstalled: deploy.CheckServerInstalled(d.cfg.InstallDir),
+		OxideInstalled:  oxide.CheckOxideInstalled(d.cfg.InstallDir),
 	}
 
 	data, err := json.Marshal(payload)