Function updateFileHistoryState

src/screens/REPL.tsx:2947–2956

(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);