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/deploy_windows.go

@@ -0,0 +1,145 @@
+//go:build windows
+
+package deploy
+
+import (
+	"archive/zip"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"os/exec"
+	"path/filepath"
+)
+
+// InstallSteamCMD downloads and installs SteamCMD for Windows into the given
+// install directory. If SteamCMD is already present it returns the existing
+// path without re-downloading. The returned string is the absolute path to
+// steamcmd.exe.
+func InstallSteamCMD(installDir string) (string, error) {
+	steamcmdDir := filepath.Join(installDir, "steamcmd")
+	steamcmdPath := filepath.Join(steamcmdDir, "steamcmd.exe")
+
+	// Already installed — nothing to do.
+	if _, err := os.Stat(steamcmdPath); err == nil {
+		log.Printf("SteamCMD already installed at %s", steamcmdPath)
+		return steamcmdPath, nil
+	}
+
+	if err := os.MkdirAll(steamcmdDir, 0755); err != nil {
+		return "", fmt.Errorf("failed to create steamcmd directory %s: %w", steamcmdDir, err)
+	}
+
+	// Download the Windows zip.
+	zipPath := filepath.Join(steamcmdDir, "steamcmd.zip")
+	if err := downloadFile("https://steamcdn-a.akamaihd.net/client/installer/steamcmd.zip", zipPath); err != nil {
+		return "", fmt.Errorf("failed to download steamcmd: %w", err)
+	}
+
+	// Extract the zip into steamcmdDir.
+	if err := extractZip(zipPath, steamcmdDir); err != nil {
+		return "", fmt.Errorf("failed to extract steamcmd.zip: %w", err)
+	}
+
+	// Verify the exe landed where expected.
+	if _, err := os.Stat(steamcmdPath); err != nil {
+		return "", fmt.Errorf("steamcmd.exe not found after extraction: %w", err)
+	}
+
+	log.Printf("SteamCMD installed successfully at %s", steamcmdPath)
+	return steamcmdPath, nil
+}
+
+// RegisterService creates a Windows service for the Rust Dedicated Server
+// using sc.exe. If the caller does not have administrator privileges the
+// command will fail silently with a warning log.
+func RegisterService(installDir string, cfg DeployConfig) error {
+	serverPath := filepath.Join(installDir, "server", "RustDedicated.exe")
+
+	binPath := fmt.Sprintf(`"%s" -batchmode +server.hostname "%s" +server.port %d +rcon.port %d +rcon.password "%s" +rcon.web 1 +server.identity "corrosion" +server.maxplayers %d +server.worldsize %d +server.seed %d`,
+		serverPath, cfg.ServerName, cfg.ServerPort, cfg.RconPort,
+		cfg.RconPassword, cfg.MaxPlayers, cfg.WorldSize, cfg.Seed)
+
+	cmd := exec.Command("sc.exe", "create", "RustServer", "binPath=", binPath, "start=", "auto")
+	if out, err := cmd.CombinedOutput(); err != nil {
+		log.Printf("WARNING: sc.exe create failed (may require admin): %v — output: %s", err, string(out))
+	} else {
+		log.Println("Windows service RustServer registered successfully")
+	}
+
+	return nil
+}
+
+// downloadFile fetches url and writes the response body to dest on disk.
+func downloadFile(url, dest string) error {
+	resp, err := http.Get(url)
+	if err != nil {
+		return fmt.Errorf("GET %s failed: %w", url, err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("GET %s returned status %d", url, resp.StatusCode)
+	}
+
+	out, err := os.Create(dest)
+	if err != nil {
+		return fmt.Errorf("failed to create file %s: %w", dest, err)
+	}
+	defer out.Close()
+
+	if _, err := io.Copy(out, resp.Body); err != nil {
+		return fmt.Errorf("failed to write to %s: %w", dest, err)
+	}
+
+	return nil
+}
+
+// extractZip extracts all files from a zip archive into destDir, preserving
+// the directory structure from the archive.
+func extractZip(zipPath, destDir string) error {
+	r, err := zip.OpenReader(zipPath)
+	if err != nil {
+		return fmt.Errorf("failed to open zip %s: %w", zipPath, err)
+	}
+	defer r.Close()
+
+	for _, f := range r.File {
+		target := filepath.Join(destDir, f.Name)
+
+		if f.FileInfo().IsDir() {
+			if err := os.MkdirAll(target, 0755); err != nil {
+				return fmt.Errorf("failed to create directory %s: %w", target, err)
+			}
+			continue
+		}
+
+		// Ensure the parent directory exists.
+		if err := os.MkdirAll(filepath.Dir(target), 0755); err != nil {
+			return fmt.Errorf("failed to create parent dir for %s: %w", target, err)
+		}
+
+		rc, err := f.Open()
+		if err != nil {
+			return fmt.Errorf("failed to open zip entry %s: %w", f.Name, err)
+		}
+
+		outFile, err := os.Create(target)
+		if err != nil {
+			rc.Close()
+			return fmt.Errorf("failed to create file %s: %w", target, err)
+		}
+
+		if _, err := io.Copy(outFile, rc); err != nil {
+			outFile.Close()
+			rc.Close()
+			return fmt.Errorf("failed to extract %s: %w", f.Name, err)
+		}
+
+		outFile.Close()
+		rc.Close()
+	}
+
+	return nil
+}