feat: add file logging to %APPDATA%\Wraith\wraith.log for headless debugging

slog now writes to wraith.log instead of stdout. Debug-level logging enabled.
ConnectSSH and UpdateConnection log credential resolution details. This lets
us diagnose the pubkey auth issue without needing a console window.

Check: %APPDATA%\Wraith\wraith.log after attempting a connection.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/connections/service.go

@@ -4,6 +4,7 @@ import (
 	"database/sql"
 	"encoding/json"
 	"fmt"
+	"log/slog"
 	"strings"
 	"time"
 )
@@ -311,6 +312,12 @@ func scanConnections(rows *sql.Rows) ([]Connection, error) {
 }
 
 func (s *ConnectionService) UpdateConnection(id int64, input UpdateConnectionInput) (*Connection, error) {
+	slog.Info("UpdateConnection called",
+		"id", id,
+		"name", input.Name,
+		"credentialID", input.CredentialID,
+		"groupID", input.GroupID,
+	)
 	setClauses := []string{"updated_at = CURRENT_TIMESTAMP"}
 	args := []interface{}{}
 
@@ -330,9 +337,13 @@ func (s *ConnectionService) UpdateConnection(id int64, input UpdateConnectionInp
 		setClauses = append(setClauses, "group_id = ?")
 		args = append(args, *input.GroupID)
 	}
-	if input.CredentialID != nil {
+	// Always update credential_id — nil clears it, non-nil sets it.
+	// Unlike other fields, credential assignment is explicit on every save.
 	setClauses = append(setClauses, "credential_id = ?")
+	if input.CredentialID != nil {
 		args = append(args, *input.CredentialID)
+	} else {
+		args = append(args, nil)
 	}
 	if input.Tags != nil {
 		tags, _ := json.Marshal(input.Tags)

main.go

@@ -4,6 +4,8 @@ import (
 	"embed"
 	"log"
 	"log/slog"
+	"os"
+	"path/filepath"
 
 	wraithapp "github.com/vstockwell/wraith/internal/app"
 	"github.com/wailsapp/wails/v3/pkg/application"
@@ -16,7 +18,11 @@ var version = "dev"
 var assets embed.FS
 
 func main() {
-	slog.Info("starting Wraith")
+	// Set up file logging so we can debug without a console window
+	if logFile := setupFileLogging(); logFile != nil {
+		defer logFile.Close()
+	}
+	slog.Info("starting Wraith", "version", version)
 
 	wraith, err := wraithapp.New(version)
 	if err != nil {
@@ -57,3 +63,29 @@ func main() {
 		log.Fatal(err)
 	}
 }
+
+// setupFileLogging configures slog to write to %APPDATA%\Wraith\wraith.log (Windows)
+// or ~/.local/share/wraith/wraith.log (macOS/Linux). Returns the file handle for deferred close.
+func setupFileLogging() *os.File {
+	var logDir string
+	if appData := os.Getenv("APPDATA"); appData != "" {
+		logDir = filepath.Join(appData, "Wraith")
+	} else if home, err := os.UserHomeDir(); err == nil {
+		logDir = filepath.Join(home, ".local", "share", "wraith")
+	} else {
+		return nil
+	}
+
+	os.MkdirAll(logDir, 0755)
+	logPath := filepath.Join(logDir, "wraith.log")
+
+	f, err := os.OpenFile(logPath, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
+	if err != nil {
+		return nil
+	}
+
+	handler := slog.NewTextHandler(f, &slog.HandlerOptions{Level: slog.LevelDebug})
+	slog.SetDefault(slog.New(handler))
+	log.SetOutput(f)
+	return f
+}