#27983 acpmux tests: allow the CPU-class test's hermetic host launcher in the daemon guard

Base red fix. hermetic_daemon_guard::only_the_hermetic_helper_starts_the_acpmux_binary fails on feat-cmux-next:

tests/cpu_class.rs:175: let launcher = HostLauncher { exe: daemon_env::bin().into(), prefix: Vec::new() };

#27600 added tests/cpu_class.rs, which starts the agent host the same way agent_host.rs and cwd_pin.rs already do: the child gets daemon_env::vars(..) as SpawnSpec.env, never the host environment. The guard was never told about the new file. This adds it to the allowlist, with the same comment as the existing entries.

Risk: low. Test-only, one allowlist entry.

Validation

• Red on base: fleet cmux-ci run 41002680839 (cargo test -p acpmux) fails this test at line 76.
• Green with this change: fleet run 41004384235, cargo test -p acpmux --test hermetic_daemon_guard: 2 passed.

Agent session: agent session

🤖 Generated with Claude Code

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Summary by cubic

Fixes the hermetic_daemon_guard test failing on feat-cmux-next by adding the CPU-class test's HostLauncher to the guard's allowlist. The test added in #27600 starts the host the same way agent_host.rs and cwd_pin.rs do, but was never listed. Test-only change with no runtime impact.