chore: modernize workflows, security scanning, and linting configuration (#50)

* build: update Go 1.25, CI workflows, and build tooling

- Upgrade to Go 1.25
- Add benchmark targets to Makefile
- Implement parallel gosec execution
- Lock tool versions for reproducibility
- Add shellcheck directives to scripts
- Update CI workflows with improved caching

* refactor: migrate from golangci-lint to revive

- Replace golangci-lint with revive for linting
- Configure comprehensive revive rules
- Fix all EditorConfig violations
- Add yamllint and yamlfmt support
- Remove deprecated .golangci.yml

* refactor: rename utils to shared and deduplicate code

- Rename utils package to shared
- Add shared constants package
- Deduplicate constants across packages
- Address CodeRabbit review feedback

* fix: resolve SonarQube issues and add safety guards

- Fix all 73 SonarQube OPEN issues
- Add nil guards for resourceMonitor, backpressure, metricsCollector
- Implement io.Closer for headerFileReader
- Propagate errors from processing helpers
- Add metrics and templates packages
- Improve error handling across codebase

* test: improve test infrastructure and coverage

- Add benchmarks for cli, fileproc, metrics
- Improve test coverage for cli, fileproc, config
- Refactor tests with helper functions
- Add shared test constants
- Fix test function naming conventions
- Reduce cognitive complexity in benchmark tests

* docs: update documentation and configuration examples

- Update CLAUDE.md with current project state
- Refresh README with new features
- Add usage and configuration examples
- Add SonarQube project configuration
- Consolidate config.example.yaml

* fix: resolve shellcheck warnings in scripts

- Use ./*.go instead of *.go to prevent dash-prefixed filenames
  from being interpreted as options (SC2035)
- Remove unreachable return statement after exit (SC2317)
- Remove obsolete gibidiutils/ directory reference

* chore(deps): upgrade go dependencies

* chore(lint): megalinter fixes

* fix: improve test coverage and fix file descriptor leaks

- Add defer r.Close() to fix pipe file descriptor leaks in benchmark tests
- Refactor TestProcessorConfigureFileTypes with helper functions and assertions
- Refactor TestProcessorLogFinalStats with output capture and keyword verification
- Use shared constants instead of literal strings (TestFilePNG, FormatMarkdown, etc.)
- Reduce cognitive complexity by extracting helper functions

* fix: align test comments with function names

Remove underscores from test comments to match actual function names:
- benchmark/benchmark_test.go (2 fixes)
- fileproc/filetypes_config_test.go (4 fixes)
- fileproc/filetypes_registry_test.go (6 fixes)
- fileproc/processor_test.go (6 fixes)
- fileproc/resource_monitor_types_test.go (4 fixes)
- fileproc/writer_test.go (3 fixes)

* fix: various test improvements and bug fixes

- Remove duplicate maxCacheSize check in filetypes_registry_test.go
- Shorten long comment in processor_test.go to stay under 120 chars
- Remove flaky time.Sleep in collector_test.go, use >= 0 assertion
- Close pipe reader in benchmark_test.go to fix file descriptor leak
- Use ContinueOnError in flags_test.go to match ResetFlags behavior
- Add nil check for p.ui in processor_workers.go before UpdateProgress
- Fix resource_monitor_validation_test.go by setting hardMemoryLimitBytes directly

* chore(yaml): add missing document start markers

Add --- document start to YAML files to satisfy yamllint:
- .github/workflows/codeql.yml
- .github/workflows/build-test-publish.yml
- .github/workflows/security.yml
- .github/actions/setup/action.yml

* fix: guard nil resourceMonitor and fix test deadlock

- Guard resourceMonitor before CreateFileProcessingContext call
- Add ui.UpdateProgress on emergency stop and path error returns
- Fix potential deadlock in TestProcessFile using wg.Go with defer close

config/loader_test.go

@@ -7,6 +7,7 @@ import (
 	"github.com/spf13/viper"
 
 	"github.com/ivuorinen/gibidify/config"
+	"github.com/ivuorinen/gibidify/shared"
 	"github.com/ivuorinen/gibidify/testutil"
 )
 
@@ -26,14 +27,14 @@ func TestDefaultConfig(t *testing.T) {
 	testutil.ResetViperConfig(t, tmpDir)
 
 	// Check defaults
-	defaultSizeLimit := config.GetFileSizeLimit()
+	defaultSizeLimit := config.FileSizeLimit()
 	if defaultSizeLimit != defaultFileSizeLimit {
 		t.Errorf("Expected default file size limit of 5242880, got %d", defaultSizeLimit)
 	}
 
-	ignoredDirs := config.GetIgnoredDirectories()
+	ignoredDirs := config.IgnoredDirectories()
 	if len(ignoredDirs) == 0 {
-		t.Errorf("Expected some default ignored directories, got none")
+		t.Error("Expected some default ignored directories, got none")
 	}
 
 	// Restore Viper state
@@ -76,13 +77,11 @@ ignoreDirectories:
 // TestLoadConfigWithValidation tests that invalid config files fall back to defaults.
 func TestLoadConfigWithValidation(t *testing.T) {
 	// Create a temporary config file with invalid content
-	configContent := `
-fileSizeLimit: 100
-ignoreDirectories:
-	- node_modules
-	- ""
-	- .git
-`
+	configContent := "fileSizeLimit: 100\n" +
+		"ignoreDirectories:\n" +
+		"- node_modules\n" +
+		"- \"\"\n" +
+		"- .git\n"
 
 	tempDir := t.TempDir()
 	configFile := tempDir + "/config.yaml"
@@ -100,13 +99,13 @@ ignoreDirectories:
 	config.LoadConfig()
 
 	// Should have fallen back to defaults due to validation failure
-	if config.GetFileSizeLimit() != int64(config.DefaultFileSizeLimit) {
-		t.Errorf("Expected default file size limit after validation failure, got %d", config.GetFileSizeLimit())
+	if config.FileSizeLimit() != int64(shared.ConfigFileSizeLimitDefault) {
+		t.Errorf("Expected default file size limit after validation failure, got %d", config.FileSizeLimit())
 	}
-	if containsString(config.GetIgnoredDirectories(), "") {
+	if containsString(config.IgnoredDirectories(), "") {
 		t.Errorf(
 			"Expected ignored directories not to contain empty string after validation failure, got %v",
-			config.GetIgnoredDirectories(),
+			config.IgnoredDirectories(),
 		)
 	}
 }
@@ -119,5 +118,6 @@ func containsString(slice []string, item string) bool {
 			return true
 		}
 	}
+
 	return false
 }