Fix port detection and manual forwarding issues

Major improvements to error handling and debugging:

- Fix program quitting on manual port forwarding errors
- Add comprehensive debug logging for SSH connections
- Improve error handling to show messages instead of quitting
- Add StateStartingForward for better user feedback
- Enhanced SSH client creation with default key loading
- Add --test-connect mode for debugging specific hosts
- Better timeout handling and connection diagnostics

The application now gracefully handles connection failures and
provides helpful error messages instead of crashing.

Co-authored-by: Ona <no-reply@ona.com>

main.go

@@ -12,6 +12,12 @@ func main() {
 		return
 	}
 	
+	// Check for connection test mode
+	if len(os.Args) > 2 && os.Args[1] == "--test-connect" {
+		testConnection(os.Args[2])
+		return
+	}
+	
 	// Initialize the application
 	app := NewApp()
 	if err := app.Run(); err != nil {
@@ -51,4 +57,54 @@ func testMode() {
 	fmt.Println("")
 	fmt.Println("To run the interactive TUI, use: ./kport")
 	fmt.Println("Note: TUI requires a proper terminal environment")
+	fmt.Println("")
+	fmt.Println("To test connection to a specific host: ./kport --test-connect <hostname>")
+}
+
+// testConnection tests connecting to a specific host
+func testConnection(hostName string) {
+	fmt.Printf("Testing connection to host: %s\n", hostName)
+	fmt.Println("=====================================")
+	
+	// Load SSH config
+	config := NewSSHConfig()
+	if err := config.LoadConfig(); err != nil {
+		fmt.Printf("❌ Failed to load SSH config: %v\n", err)
+		return
+	}
+	
+	// Find the host
+	host, err := config.GetHostByName(hostName)
+	if err != nil {
+		fmt.Printf("❌ Host not found: %v\n", err)
+		return
+	}
+	
+	fmt.Printf("Found host configuration:\n")
+	fmt.Printf("  Name: %s\n", host.Name)
+	fmt.Printf("  Hostname: %s\n", host.Hostname)
+	fmt.Printf("  User: %s\n", host.User)
+	fmt.Printf("  Port: %s\n", host.Port)
+	if host.Identity != "" {
+		fmt.Printf("  Identity: %s\n", host.Identity)
+	}
+	fmt.Println("")
+	
+	// Test port detection
+	fmt.Println("Testing port detection...")
+	ports, err := detectRemotePorts(*host)
+	if err != nil {
+		fmt.Printf("❌ Port detection failed: %v\n", err)
+		fmt.Println("")
+		fmt.Println("This is expected if:")
+		fmt.Println("- The host is not reachable")
+		fmt.Println("- SSH keys are not set up")
+		fmt.Println("- SSH agent is not running")
+		fmt.Println("- The host doesn't exist")
+	} else {
+		fmt.Printf("✅ Port detection successful! Found %d ports: %v\n", len(ports), ports)
+	}
+	
+	fmt.Println("")
+	fmt.Println("You can still use manual port forwarding in the TUI even if port detection fails.")
 }