Fix linter issues and test failures

- Fix spelling: cancelled → canceled, cancelling → canceling
- Remove unused error return from performFlush() function
- Check cmd.Help() error return in search.go
- Fix file permissions in gitignore.go (0644 → 0600)
- Update tests to match performFlush signature change
- Remove unused os import from flush_manager.go

cmd/bd/doctor.go

@@ -165,7 +165,7 @@ func applyFixes(result doctorResult) {
 
 	response = strings.TrimSpace(strings.ToLower(response))
 	if response != "" && response != "y" && response != "yes" {
-		fmt.Println("Fix cancelled.")
+		fmt.Println("Fix canceled.")
 		return
 	}