feat: add custom patterns directory support with environment variable configuration

## CHANGES

- Add custom patterns directory support via environment variable
- Implement custom patterns plugin with registry integration
- Override main patterns with custom directory patterns
- Expand home directory paths in custom patterns config
- Add comprehensive test coverage for custom patterns functionality
- Integrate custom patterns into plugin setup workflow
- Support pattern precedence with custom over main patterns

plugins/tools/custom_patterns/custom_patterns.go

@@ -0,0 +1,61 @@
+package custom_patterns
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/danielmiessler/fabric/plugins"
+)
+
+func NewCustomPatterns() (ret *CustomPatterns) {
+	label := "Custom Patterns"
+	ret = &CustomPatterns{}
+
+	ret.PluginBase = &plugins.PluginBase{
+		Name:             label,
+		SetupDescription: "Custom Patterns - Set directory for your custom patterns (optional)",
+		EnvNamePrefix:    plugins.BuildEnvVariablePrefix(label),
+		ConfigureCustom:  ret.configure,
+	}
+
+	ret.CustomPatternsDir = ret.AddSetupQuestionCustom("Directory", false,
+		"Enter the path to your custom patterns directory (leave empty to skip)")
+
+	return
+}
+
+type CustomPatterns struct {
+	*plugins.PluginBase
+	CustomPatternsDir *plugins.SetupQuestion
+}
+
+func (o *CustomPatterns) configure() error {
+	if o.CustomPatternsDir.Value != "" {
+		// Expand home directory if needed
+		if strings.HasPrefix(o.CustomPatternsDir.Value, "~/") {
+			if homeDir, err := os.UserHomeDir(); err == nil {
+				o.CustomPatternsDir.Value = filepath.Join(homeDir, o.CustomPatternsDir.Value[2:])
+			}
+		}
+
+		// Convert to absolute path
+		if absPath, err := filepath.Abs(o.CustomPatternsDir.Value); err == nil {
+			o.CustomPatternsDir.Value = absPath
+		}
+
+		// Create the directory if it doesn't exist
+		if err := os.MkdirAll(o.CustomPatternsDir.Value, 0755); err != nil {
+			// If we can't create it, clear the value to avoid errors
+			o.CustomPatternsDir.Value = ""
+		}
+	}
+
+	return nil
+}
+
+// IsConfigured returns true if a custom patterns directory has been set
+func (o *CustomPatterns) IsConfigured() bool {
+	// Check if the plugin has been configured with a directory
+	return o.CustomPatternsDir.Value != ""
+}