fix: address review feedback

- Remove redundant newline from fmt.Println at line 325
- Add 9 comprehensive VersionConflictError tests to event_test.go:
  * Error message formatting with context fields
  * Field accessibility (ActorID, AttemptedVersion, CurrentVersion)
  * Unwrap() method and error wrapping
  * Sentinel error checking with errors.Is()
  * Type assertion support with errors.As()
  * Retry logic extraction of CurrentVersion
  * Special character handling in ActorID

Co-Authored-By: Claude Code <noreply@anthropic.com>

examples/version_conflict_retry.go

@@ -322,7 +322,7 @@ func main() {
 	eventStore := store.NewInMemoryEventStore()
 	actorID := "order-123"
 
-	fmt.Println("=== Version Conflict Retry Patterns ===\n")
+	fmt.Println("=== Version Conflict Retry Patterns ===")
 
 	// Demonstrate patterns (using simplified versions)
 	log.Println("Pattern 1: Simple Exponential Backoff")