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_test.go

@@ -0,0 +1,79 @@
+package custom_patterns
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewCustomPatterns(t *testing.T) {
+	plugin := NewCustomPatterns()
+
+	assert.NotNil(t, plugin)
+	assert.Equal(t, "Custom Patterns", plugin.GetName())
+	assert.Equal(t, "Custom Patterns - Set directory for your custom patterns (optional)", plugin.GetSetupDescription())
+	assert.False(t, plugin.IsConfigured()) // Should not be configured initially
+}
+func TestCustomPatterns_Configure(t *testing.T) {
+	plugin := NewCustomPatterns()
+
+	// Test with empty directory (should work)
+	plugin.CustomPatternsDir.Value = ""
+	err := plugin.configure()
+	assert.NoError(t, err)
+
+	// Test with home directory expansion
+	plugin.CustomPatternsDir.Value = "~/test-patterns"
+	err = plugin.configure()
+	assert.NoError(t, err)
+
+	homeDir, _ := os.UserHomeDir()
+	expectedPath := filepath.Join(homeDir, "test-patterns")
+	absExpected, _ := filepath.Abs(expectedPath)
+	assert.Equal(t, absExpected, plugin.CustomPatternsDir.Value)
+
+	// Clean up
+	os.RemoveAll(plugin.CustomPatternsDir.Value)
+}
+
+func TestCustomPatterns_ConfigureWithTempDir(t *testing.T) {
+	plugin := NewCustomPatterns()
+
+	// Test with a temporary directory
+	tmpDir, err := os.MkdirTemp("", "test-custom-patterns-*")
+	require.NoError(t, err)
+	defer os.RemoveAll(tmpDir)
+
+	plugin.CustomPatternsDir.Value = tmpDir
+	err = plugin.configure()
+	assert.NoError(t, err)
+
+	absPath, _ := filepath.Abs(tmpDir)
+	assert.Equal(t, absPath, plugin.CustomPatternsDir.Value)
+
+	// Verify directory exists
+	info, err := os.Stat(plugin.CustomPatternsDir.Value)
+	assert.NoError(t, err)
+	assert.True(t, info.IsDir())
+
+	// Should be configured now
+	assert.True(t, plugin.IsConfigured())
+}
+
+func TestCustomPatterns_IsConfigured(t *testing.T) {
+	plugin := NewCustomPatterns()
+
+	// Initially not configured
+	assert.False(t, plugin.IsConfigured())
+
+	// Set a directory
+	plugin.CustomPatternsDir.Value = "/some/path"
+	assert.True(t, plugin.IsConfigured())
+
+	// Clear the directory
+	plugin.CustomPatternsDir.Value = ""
+	assert.False(t, plugin.IsConfigured())
+}