The monitoring export contains overlapping observation intervals. Finish the coverage calculation so the report measures time actually covered instead of adding duplicate coverage more than once.
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 is a list of half-open integer intervals [start,end]. Reject reversed intervals, ignore zero-length intervals, and merge overlaps and touching endpoints. Return intervals sorted by start and duration as the sum of merged lengths. Negative endpoints are valid.
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.