fix(install): don't let outer ERR trap mask first_time_install.sh failures

set +e alone doesn't suppress bash's ERR trap, so any non-zero exit from
first_time_install.sh inside the one-shot installer immediately triggered
the outer on_error handler with a generic "Main installation, line 370"
message — before the script could report the real exit code or point to
logs/. Suspend the trap for that block so the existing if/else handling
runs instead.

scripts/install/one-shot-install.sh

@@ -340,8 +340,13 @@ main() {
     echo ""
     
     # Execute with proper error handling and non-interactive mode
-    # Temporarily disable errexit to capture exit code instead of exiting immediately
+    # Temporarily disable errexit AND the ERR trap to capture exit code instead of
+    # exiting immediately. `set +e` alone does not suppress the ERR trap, so without
+    # `trap '' ERR` a non-zero exit from first_time_install.sh would trigger on_error
+    # here with the generic "Main installation" message instead of the detailed
+    # if/else handling below.
     set +e
+    trap '' ERR
 
     # Check /tmp permissions - only fix if actually wrong (common in automated scenarios)
     # When running manually, /tmp usually has correct permissions (1777)
@@ -370,6 +375,7 @@ main() {
         sudo -E env TMPDIR=/tmp LEDMATRIX_ASSUME_YES=1 bash ./first_time_install.sh -y </dev/null
     fi
     INSTALL_EXIT_CODE=$?
+    trap 'on_error $LINENO' ERR  # Re-enable ERR trap
     set -e  # Re-enable errexit
     
     if [ $INSTALL_EXIT_CODE -eq 0 ]; then