Flaky CI: cli-mosquitto base:trixie arm64 leg hangs after "Container started" until the 30-minute timeout #8

Context

On PR #5, the CI leg test (cli-mosquitto, base:trixie, arm64) hung silently after "Container started" until the 30-minute job timeout, then passed on rerun. It has happened once so far. On Debian, cli-mosquitto installs from repo.mosquitto.org, so the hang may be network-side, but the cause hasn't been investigated.

Items

• Watch for a repeat of this hang on the cli-mosquitto arm64 legs.
• If it recurs, add a per-step timeout to the features test job so a hang fails fast instead of burning 30 minutes.
• If it recurs, investigate repo.mosquitto.org fetches on arm64 (slow mirror, stalled apt download).

Pointers

• PR feat(release): publish to GHCR with GITHUB_TOKEN when the registry secrets are empty (DF15b) #5, run 40771188303, attempt 1 (hung); the rerun passed.
• .github/workflows/features.yml (test matrix)
• src/cli-mosquitto/install.sh, test/cli-mosquitto/

From the devcontainer-features plan close-out (2026-10-29).