Improve bin/verify-exercises failure handling

[ageron]

Continue after failures and summarize them at the end, support multiple exercise globs, time out frozen tests after 30 seconds, and handle Ctrl-C reliably.

[Anton-4]

Thanks @ageron, I did not spot any issues but Claude did 😄 :

Findings

1. The timeout and the Ctrl-C trap kill only the direct roc PID, not its descendants

run_tests:102, stop_test:67

Verified: with a stub that hangs in a child process, the timeout fires and
reports correctly, but the grandchild survives the run:

roc test timed out after 2 seconds.
--- leftover processes: ---
 2311    00:02 sleep 600

Same on Ctrl-C. This is a regression for the Ctrl-C case. On main,
roc test ran in the foreground, so the terminal's process-group SIGINT reached
the whole tree — I confirmed the old script leaves nothing behind. The PR moves
it to a background job, and bash sets SIGINT to SIG_IGN for background jobs in
a non-interactive shell; that ignore is inherited by its children, so the group
signal now reaches nothing and the trap's kill -KILL $roc_pid covers only the
top process. So the PR trades cleaner exit-status reporting (130 instead of dying
by signal) for a leaked process tree.

Fix I tested and confirmed reaps everything — enable job control so the job gets
its own pgid, then kill the group:

set -m
FORCE_COLOR=1 roc test ${opts} "${test_file}" &
roc_pid=$!
set +m
# then, in stop_test and in the watchdog:
kill -KILL -- "-${roc_pid}" 2>/dev/null || true

CI already apt-get installs coreutils, so timeout -k 5 30 roc test … would
also replace ~50 lines — but it isn't in the macOS base system, which I assume is
why you hand-rolled it. Your call.

2. if verify_exercise … silently disables set -e for the entire call

verify_exercises:170

Bash suspends errexit for the whole dynamic extent of an if condition,
including functions and subshells called from it. Confirmed:

--- called bare (errexit active):      (aborts at `false`)
--- called in if condition:            REACHED-after-false   f ok

So cp -r "${dir}/." "${tmp_dir}", cd "${tmp_dir}", the jq calls and
cp "${example_file}" "${module_file}" no longer abort — a malformed
.meta/config.json now runs tests against a half-populated temp dir instead of
failing loudly. The exercise still ends up reported as failed, so this is low
severity, but explicit || exit 1 on those setup commands would restore the old
behaviour.

3. Add required_tool roc next to required_tool jq

:24

Previously a missing/broken roc stopped at the first exercise. Now it fans out
— with PATH stripped, three exercises produced three roc: command not found
lines and listed all three as failed. Across ~90 exercises that buries the real
cause. One line fixes it.

[ageron]

Thanks @Anton-4, I worked with Sol 5.6, apparently not quite as smart as Claude. So I just switched to Terra, and it fixed the issues. 👍

[Anton-4]

Thanks @ageron!