The stock ledger needs to replay transfers in their original order. Implement the balance updates so an invalid transfer cannot leave one warehouse debited without the matching credit.
Build the implementation in C# 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 stock mapping warehouse names to nonnegative integer counts and transfers containing from, to and positive integer quantity. Process in order; unknown warehouses, invalid quantities or insufficient stock must be rejected. A self-transfer still requires sufficient stock but leaves it unchanged. Return final stock sorted by warehouse.
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.