refactor: major codebase improvements and test framework overhaul

This commit represents a comprehensive refactoring of the codebase focused on
improving code quality, testability, and maintainability.

Key improvements:
- Implement dependency injection and interface-based architecture
- Add comprehensive test framework with fixtures and test suites
- Fix all linting issues (errcheck, gosec, staticcheck, goconst, etc.)
- Achieve full EditorConfig compliance across all files
- Replace hardcoded test data with proper fixture files
- Add configuration loader with hierarchical config support
- Improve error handling with contextual information
- Add progress indicators for better user feedback
- Enhance Makefile with help system and improved editorconfig commands
- Consolidate constants and remove deprecated code
- Strengthen validation logic for GitHub Actions
- Add focused consumer interfaces for better separation of concerns

Testing improvements:
- Add comprehensive integration tests
- Implement test executor pattern for better test organization
- Create extensive YAML fixture library for testing
- Fix all failing tests and improve test coverage
- Add validation test fixtures to avoid embedded YAML in Go files

Build and tooling:
- Update Makefile to show help by default
- Fix editorconfig commands to use eclint properly
- Add comprehensive help documentation to all make targets
- Improve file selection patterns to avoid glob errors

This refactoring maintains backward compatibility while significantly
improving the internal architecture and developer experience.

internal/internal_parser_test.go

@@ -2,16 +2,19 @@ package internal
 
 import (
 	"testing"
+
+	"github.com/ivuorinen/gh-action-readme/testutil"
 )
 
 func TestParseActionYML_Valid(t *testing.T) {
-	path := "../testdata/example-action/action.yml"
-	action, err := ParseActionYML(path)
+	// Create temporary action file using fixture
+	actionPath := testutil.CreateTemporaryAction(t, "actions/javascript/simple.yml")
+	action, err := ParseActionYML(actionPath)
 	if err != nil {
 		t.Fatalf("failed to parse action.yml: %v", err)
 	}
-	if action.Name != "Example Action" {
-		t.Errorf("expected name 'Example Action', got '%s'", action.Name)
+	if action.Name != "Simple JavaScript Action" {
+		t.Errorf("expected name 'Simple JavaScript Action', got '%s'", action.Name)
 	}
 	if action.Description == "" {
 		t.Error("expected non-empty description")