The same row and column pair can appear more than once in an export. Build the pivot result so repeated observations are aggregated and missing cells have the defined representation.
Build the implementation in SQL 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 is a list of records with string row, string column and integer value. Sum duplicates. Return sorted rows, sorted columns and a dense matrix using zero for missing cells. Zero-sum cells still retain their row and column labels. Reject boolean or noninteger values.
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.