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/search.go

@@ -41,10 +41,9 @@ Examples:
 		// If no query provided, show help
 		if query == "" {
 			fmt.Fprintf(os.Stderr, "Error: search query is required\n")
-			// #nosec G104 -- cmd.Help() error intentionally ignored. We're already in an
-			// error path (missing query) and will exit(1) regardless. Help() errors are
-			// rare (I/O failures) and don't affect the outcome. See TestSearchCommand_HelpErrorHandling
-			cmd.Help()
+			if err := cmd.Help(); err != nil {
+				fmt.Fprintf(os.Stderr, "Error displaying help: %v\n", err)
+			}
 			os.Exit(1)
 		}