fix(tokens): set +e in test.sh silently swallows curl failures in demo script

[Prachi194agrawal]

Bug Description

samples/tokens/scripts/test.sh uses set +e at the script entry point, which
instructs bash to ignore all non-zero exit codes. Combined with trap exit 1 INT
(which only catches Ctrl+C), this means every curl -f call inside run_test() can
fail silently — the script continues executing subsequent steps and exits with code 0,
falsely reporting the demo as successful.

Affected File

samples/tokens/scripts/test.sh

Root Cause

Line 64 (original):

set +e              # ← errors ignored
set -o pipefail
trap exit 1 INT     # ← only handles Ctrl+C, not curl failures

When curl -f returns a non-zero exit code (e.g. HTTP 4xx/5xx or connection refused),
bash ignores it under set +e and moves to the next command.

Proof (terminal reproduction)

# With set +e (original behaviour): failure is swallowed
set +e
curl -f -sS http://127.0.0.1:1 >/dev/null
echo "curl_exit=$?"               # curl_exit=7
echo "continued_after_failure=yes" # continued_after_failure=yes ← BUG

# With set -e (fixed behaviour): script stops on failure
bash -c 'set -e; curl -f -sS http://127.0.0.1:1 >/dev/null; echo "continued=yes"'
# subshell_exit=7   ← execution halted correctly, "continued=yes" never printed

Impact

• The token issue step (POST /issuer/issue) can fail and the script still proceeds
  to transfer and balance-check calls, which then operate on a non-existent token.
• Demo output appears to succeed (exit 0) even when the network is broken.
• CI/CD pipelines using make test would never catch integration failures.

Fix

Replace set +e with set -e, upgrade the trap to handle ERR (any error) in
addition to INT (Ctrl+C), and guard the cleanup() function against recursive
trap firing:

# Script Start
set -e
set -o pipefail
trap cleanup INT ERR

...

function cleanup() {
    trap - INT ERR   # prevent recursive trap
    set +e
    stop_network
    exit 1
}

Diff Summary

	Before	After
Error mode	set +e (ignore errors)	set -e (exit on error)
Trap signals	trap exit 1 INT	trap cleanup INT ERR
cleanup() guard	missing	trap - INT ERR added

[Prachi194agrawal]

I'd like to work on this issue. Could you please assign it to me?