The shutdown planner must stop selected process subtrees without stopping a parent before its selected descendants. Implement a deterministic order that respects the process relationships.
Build the implementation in Go 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 parents mapping process names to a known parent name or null, and targets. Include each target and all descendants. Return selected names ordered by descending depth in the full forest, then name. Overlapping targets are deduplicated. Validate the whole parent forest, rejecting cycles, unknown parents or unknown targets. This produces a plan and sends no signals.
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.