[eric] build: the cancel trap fires only on INT/TERM and walks the tree; the EXIT variant flipped a green build's exit code to 1 under set -e

scripts/build-app.sh

@@ -1,11 +1,19 @@
 #!/bin/bash
 set -euo pipefail
 
-# Killing this build (Ctrl-C, or a parent that gets killed) used to orphan electron-builder's 7za
-# child, which then sat for HOURS holding a ~300MB archive open (found one aged 20h). Run in our own
-# process group and sweep it on any exit so a cancelled build takes its whole tree with it (ENG-247).
-set -m
-trap 'pkill -P $$ 2>/dev/null; kill -- -$$ 2>/dev/null' EXIT INT TERM
+# Killing this build (Ctrl-C, pkill) used to orphan electron-builder's 7za child, which then sat
+# for HOURS holding a ~300MB archive open (found one aged 20h). On INT/TERM, walk and kill the whole
+# descendant tree. Deliberately NOT on EXIT: a trap that fires on normal completion flips a green
+# build's exit code under set -e and publish.sh would read success as failure (ENG-247).
+kill_descendants() {
+  local pid kids
+  for pid in "$@"; do
+    kids=$(pgrep -P "$pid" 2>/dev/null || true)
+    [ -n "$kids" ] && kill_descendants $kids
+    kill -TERM "$pid" 2>/dev/null || true
+  done
+}
+trap 'kill_descendants $(pgrep -P $$ 2>/dev/null || true); exit 130' INT TERM
 
 # Master build script for the OpenSwarm desktop app.
 #