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

fileproc/resource_monitor_metrics.go

@@ -1,3 +1,4 @@
+// Package fileproc handles file processing, collection, and output formatting.
 package fileproc
 
 import (
@@ -5,9 +6,7 @@ import (
 	"sync/atomic"
 	"time"
 
-	"github.com/sirupsen/logrus"
-
-	"github.com/ivuorinen/gibidify/gibidiutils"
+	"github.com/ivuorinen/gibidify/shared"
 )
 
 // RecordFileProcessed records that a file has been successfully processed.
@@ -18,8 +17,8 @@ func (rm *ResourceMonitor) RecordFileProcessed(fileSize int64) {
 	}
 }
 
-// GetMetrics returns current resource usage metrics.
-func (rm *ResourceMonitor) GetMetrics() ResourceMetrics {
+// Metrics returns current resource usage metrics.
+func (rm *ResourceMonitor) Metrics() ResourceMetrics {
 	if !rm.enableResourceMon {
 		return ResourceMetrics{}
 	}
@@ -54,10 +53,11 @@ func (rm *ResourceMonitor) GetMetrics() ResourceMetrics {
 		FilesProcessed:      filesProcessed,
 		TotalSizeProcessed:  totalSize,
 		ConcurrentReads:     atomic.LoadInt64(&rm.concurrentReads),
+		MaxConcurrentReads:  int64(rm.maxConcurrentReads),
 		ProcessingDuration:  duration,
 		AverageFileSize:     avgFileSize,
 		ProcessingRate:      processingRate,
-		MemoryUsageMB:       gibidiutils.SafeUint64ToInt64WithDefault(m.Alloc, 0) / 1024 / 1024,
+		MemoryUsageMB:       shared.BytesToMB(m.Alloc),
 		MaxMemoryUsageMB:    int64(rm.hardMemoryLimitMB),
 		ViolationsDetected:  violations,
 		DegradationActive:   rm.degradationActive,
@@ -68,19 +68,16 @@ func (rm *ResourceMonitor) GetMetrics() ResourceMetrics {
 
 // LogResourceInfo logs current resource limit configuration.
 func (rm *ResourceMonitor) LogResourceInfo() {
+	logger := shared.GetLogger()
 	if rm.enabled {
-		logrus.Infof(
-			"Resource limits enabled: maxFiles=%d, maxTotalSize=%dMB, fileTimeout=%ds, overallTimeout=%ds",
-			rm.maxFiles,
-			rm.maxTotalSize/1024/1024,
-			int(rm.fileProcessingTimeout.Seconds()),
-			int(rm.overallTimeout.Seconds()),
-		)
-		logrus.Infof("Resource limits: maxConcurrentReads=%d, rateLimitFPS=%d, hardMemoryMB=%d",
+		logger.Infof("Resource limits enabled: maxFiles=%d, maxTotalSize=%dMB, fileTimeout=%ds, overallTimeout=%ds",
+			rm.maxFiles, rm.maxTotalSize/int64(shared.BytesPerMB), int(rm.fileProcessingTimeout.Seconds()),
+			int(rm.overallTimeout.Seconds()))
+		logger.Infof("Resource limits: maxConcurrentReads=%d, rateLimitFPS=%d, hardMemoryMB=%d",
 			rm.maxConcurrentReads, rm.rateLimitFilesPerSec, rm.hardMemoryLimitMB)
-		logrus.Infof("Resource features: gracefulDegradation=%v, monitoring=%v",
+		logger.Infof("Resource features: gracefulDegradation=%v, monitoring=%v",
 			rm.enableGracefulDegr, rm.enableResourceMon)
 	} else {
-		logrus.Info("Resource limits disabled")
+		logger.Info("Resource limits disabled")
 	}
 }