feat(log): add Logger.Debugln, expand test coverage, update Go/CI (#21)

- Add missing Logger.Debugln method (package-level Debugln existed but
  Logger type lacked it)
- Replace empty test stubs with real tests for Debug, Debugf, Info,
  Infof, Print, Printf, Notice, Warn, Warnf, Error, Errorf, Panic,
  Panicf, Panicln
- Add tests for namespace filtering, multi-namespace clients,
  namespace registry, level storage, colorize, parseLevelString,
  Broadcast, matchesNamespace, fileInfo, Logger.Debugln,
  empty namespace default
- Update go.mod to Go 1.26.1
- Update CI to actions/checkout@v4, actions/setup-go@v5, Go 1.26,
  add -race flag, trigger on pull_request
- Fix stale CRUSH.md references (Go version, CI config, stderr bug)

log/logger.go

@@ -92,6 +92,20 @@ func (l Logger) Debugf(format string, args ...any) {
 	createLog(e)
 }
 
+// Debugln prints out logs on debug level with a newline
+func (l Logger) Debugln(args ...any) {
+	output := fmt.Sprintln(args...)
+	e := Entry{
+		Timestamp: time.Now(),
+		Output:    output,
+		File:      fileInfo(2 + l.FileInfoDepth),
+		Level:     "DEBUG",
+		level:     LDebug,
+		Namespace: l.Namespace,
+	}
+	createLog(e)
+}
+
 // Info prints out logs on info level
 func (l Logger) Info(args ...any) {
 	output := fmt.Sprint(args...)