feat: Add companion agent one-click deployment + fix frontend TS errors

Go deployment orchestrator with platform-specific SteamCMD install,
Rust server download, server.cfg generation, and service registration.
Wire deploy command subscription in daemon, make GameServerPath optional,
add InstallDir config with OS-aware defaults. Fix unused imports and
WebSocket subscribe API in ServerView.

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

companion-agent/internal/deploy/config.go

@@ -0,0 +1,71 @@
+package deploy
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+// DeployConfig holds the configuration received from a NATS cmd.deploy command.
+// These fields map directly to the Rust game server settings needed for initial deployment.
+type DeployConfig struct {
+	ServerName   string `json:"server_name"`
+	MaxPlayers   int    `json:"max_players"`
+	WorldSize    int    `json:"world_size"`
+	Seed         int    `json:"seed"`
+	ServerPort   int    `json:"server_port"`
+	RconPort     int    `json:"rcon_port"`
+	RconPassword string `json:"rcon_password"`
+}
+
+// DeployStatus represents a progress update published to NATS during deployment.
+// The frontend listens on corrosion.{license_id}.deploy.status for these messages
+// to display real-time deployment progress to the user.
+type DeployStatus struct {
+	Stage     string `json:"stage"`
+	Progress  int    `json:"progress"`
+	Message   string `json:"message"`
+	Error     string `json:"error,omitempty"`
+	Timestamp string `json:"timestamp"`
+}
+
+// Valid deployment stages:
+//   downloading_steamcmd - Downloading and extracting SteamCMD
+//   installing_steamcmd  - Running SteamCMD initial setup
+//   downloading_rust     - Downloading Rust Dedicated Server via SteamCMD
+//   configuring          - Generating server.cfg and identity directories
+//   starting             - Launching the Rust server process
+//   online               - Server is running and accepting connections
+//   failed               - Deployment failed at some stage
+
+// GenerateServerCfg creates the server.cfg file for a Rust Dedicated Server.
+// It writes to {installDir}/server/server/corrosion/cfg/server.cfg, creating
+// the full directory tree if it does not already exist.
+func GenerateServerCfg(installDir string, cfg DeployConfig) error {
+	cfgDir := filepath.Join(installDir, "server", "server", "corrosion", "cfg")
+
+	if err := os.MkdirAll(cfgDir, 0755); err != nil {
+		return fmt.Errorf("failed to create cfg directory %s: %w", cfgDir, err)
+	}
+
+	content := fmt.Sprintf(`server.hostname "%s"
+server.maxplayers %d
+server.worldsize %d
+server.seed %d
+server.port %d
+rcon.port %d
+rcon.password "%s"
+rcon.web 1
+server.identity "corrosion"
+server.saveinterval 300
+`, cfg.ServerName, cfg.MaxPlayers, cfg.WorldSize, cfg.Seed,
+		cfg.ServerPort, cfg.RconPort, cfg.RconPassword)
+
+	cfgPath := filepath.Join(cfgDir, "server.cfg")
+
+	if err := os.WriteFile(cfgPath, []byte(content), 0644); err != nil {
+		return fmt.Errorf("failed to write server.cfg to %s: %w", cfgPath, err)
+	}
+
+	return nil
+}