Function updateFileHistoryState

src/screens/REPL.tsx:2445–2457

(updater: (prev: FileHistoryState) => FileHistoryState)

      messages,
      setMessages,
      updateFileHistoryState(updater: (prev: FileHistoryState) => FileHistoryState) {
        // Perf: skip the setState when the updater returns the same reference
        // (e.g. fileHistoryTrackEdit returns `state` when the file is already
        // tracked). Otherwise every no-op call would notify all store listeners.
        setAppState(prev => {
          const updated = updater(prev.fileHistory);
          if (updated === prev.fileHistory) return prev;
          return {
            ...prev,
            fileHistory: updated
          };
        });
      },
      updateAttributionState(updater: (prev: AttributionState) => AttributionState) {
        setAppState(prev => {
          const updated = updater(prev.attribution);