fix(tests): guard empty arrays, cap output, kill orphaned children

- bash 3.2: guard BLOCKERS/PATH_ARGS empty-array expansion under set -u
- run-coverage-lane: surface collectLaneFiles errors instead of throwing
- run-test-lane: cap per-file output at 1 MB; track and SIGKILL children on SIGINT/SIGTERM

plugins/subminer-workflow/skills/subminer-change-verification/scripts/verify_subminer_change.sh

@@ -255,8 +255,18 @@ write_summary_files() {
   local lane_lines
   lane_lines=$(printf '%s\n' "${SELECTED_LANES[@]}")
   printf '%s\n' "$lane_lines" >"$ARTIFACT_DIR/lanes.txt"
-  printf '%s\n' "${BLOCKERS[@]}" >"$ARTIFACT_DIR/blockers.txt"
-  printf '%s\n' "${PATH_ARGS[@]}" >"$ARTIFACT_DIR/requested-paths.txt"
+  # bash 3.2 raises "unbound variable" under set -u when expanding an empty
+  # array, so guard on length (matching the idiom used elsewhere here).
+  if [[ ${#BLOCKERS[@]} -gt 0 ]]; then
+    printf '%s\n' "${BLOCKERS[@]}" >"$ARTIFACT_DIR/blockers.txt"
+  else
+    : >"$ARTIFACT_DIR/blockers.txt"
+  fi
+  if [[ ${#PATH_ARGS[@]} -gt 0 ]]; then
+    printf '%s\n' "${PATH_ARGS[@]}" >"$ARTIFACT_DIR/requested-paths.txt"
+  else
+    : >"$ARTIFACT_DIR/requested-paths.txt"
+  fi
 
   ARTIFACT_DIR_ENV="$ARTIFACT_DIR" \
   SESSION_ID_ENV="$SESSION_ID" \