The editor history needs independent snapshots, including when a new edit follows an undo. Implement the journal so undo, redo and branching edits preserve the correct document state.
Build the implementation in TypeScript under /app, with /app/run.sh as its entry point. Read one JSON request from standard input and write one JSON result to standard output. Input has initial JSON value and operations: set with value, undo, or redo. Set records the previous state and clears redo history. Undo/redo without available history is a no-op. Return snapshots after every operation, independent of later changes. Reject unknown operations.
Reject inputs that violate an explicit validation rule with exit status 2, no standard output, and {"error":"invalid_input"} on standard error. For valid input, exit with status 0. Keep the implementation reusable for new inputs; it must work offline and must not depend on the example data being the only data it receives.
Repair or replace the unfinished /app/run.sh and add source files under /app. Malformed JSON must use the same invalid-input response. Do not read /tests or /oracle from the application.