fix(ci): raise AVM check-circuit per-tx timeout to 120s

[AztecBot]

Summary

Raise the per-input avm_check_circuit timeout from 30s to a 120s default (overridable via AVM_CHECK_CIRCUIT_TIMEOUT), so heavy AVM inputs complete with comfortable margin.

Recurred again on 2026-06-02 as CI run 26795871178 (exit code 124, head 1f6248d). It keeps recurring because this PR has the fix but remains a draft and has never been merged — next still runs the 30s limit. Same input (e2e_multiple_blobs, ~700k rows) timed out mid circuit-check; every other input passed in 3–5s. This PR was first opened for the same failure on 2026-05-29 and rebased onto next on 2026-06-01.

Root cause

yarn-project/end-to-end/bootstrap.sh:avm_check_circuit runs bb-avm avm_check_circuit on every dumped e2e AVM input in parallel, each wrapped in a per-test timeout (exec_test → timeout -v $TIMEOUT). The runner uses --halt now,fail=1, so a single timeout fails the entire job. It is not a circuit-correctness failure.

One input — the e2e_multiple_blobs tx — produces a ~700,560-row AVM trace. On the default 2 CPUs the per-input log shows trace generation alone takes ~21s, so the circuit check is killed only a few seconds in at the 30s cap:

Generating trace...
Checking circuit... (3865 MiB)            (trace gen ~21s)
Running check (with skippable) circuit over 700560 rows.
timeout: sending signal TERM to command 'bash'   (killed mid-check at 30s)

The check was progressing, not hung — it simply needs more than 30s on 2 CPUs. Every other input passed in 3–5s.

Fix

• Bump the per-check timeout to a 120s default, overridable via AVM_CHECK_CIRCUIT_TIMEOUT.
• CPU allocation stays at the default 2: parallelize runs num_cpus/2 concurrent jobs, so the runner is already sized to be fully utilized at 2 CPUs/job. Raising CPUS without lowering the job count would oversubscribe the box. Only the wall-clock budget was the constraint.

Testing

• bash -O extglob -n yarn-project/end-to-end/bootstrap.sh — passes.

Action needed: this PR is still marked draft, which is the only thing blocking the merge (GitHub returns 405 "Pull Request is still a draft"). Mark it Ready for review and it can land on next.