fix(hardware): detect Apple Silicon under Rosetta 2 in GPU probe (BE-3435)

[mattmillerai]

ELI-5

If you run an Intel-flavored Python on a modern Apple Mac (via Apple's Rosetta 2 translator), the machine lies and says it's an old Intel chip. Our hardware probe believed the lie and reported "no GPU" — even though the Mac has a perfectly capable Apple GPU. This teaches the probe to ask macOS one extra question ("am I being translated?") so it correctly recognizes the Apple chip underneath and reports its unified-memory GPU.

What & why

comfy_cli/hardware.py:_detect_gpu keyed Apple Silicon unified-memory detection on machine == 'arm64'. An x86_64 Python running under Rosetta 2 on an Apple Silicon Mac reports platform.machine() == 'x86_64', so the unified-memory block was skipped and the machine fell through to the NVIDIA/AMD probes (which find nothing) — a capable GPU reported as gpu: null.

Fix: a small _is_apple_silicon(machine) helper keeps the native arm64 fast path and, when machine != 'arm64', falls back to sysctl -n sysctl.proc_translated (via the existing _run helper). A value of '1' means the process is translated, which only happens on Apple Silicon, so the apple/unified block is used.

Notes for the reviewer

• Chesterton's Fence — this deliberately broadens an existing check. The original machine == 'arm64' guard was introduced (intentionally minimal) in the base PR feat: add cross-platform hardware block to comfy env --json (BE-3399) #562 (BE-3399); this ticket (BE-3435) is the scoped follow-up to broaden it. The old and new conditions differ only in the newly-matched state — machine != 'arm64' and proc_translated == '1', i.e. exactly Apple Silicon under Rosetta. On a genuine Intel Mac the sysctl.proc_translated OID is absent, _run returns None, None == '1' is False, so Intel behavior is unchanged (the existing test_intel_mac_has_no_apple_gpu still passes).
• Never-raise contract preserved: _is_apple_silicon only calls _run (which never raises and is timeout-bounded) plus a string compare, and it runs inside _detect_gpu's existing try/except.
• Under Rosetta, arch is still honestly reported as x86_64 (that's what the process is); only the gpu block is corrected. The model comes from machdep.cpu.brand_string, which returns the real Apple chip name even under translation.
• New unit test mocks _run to return '1' for the sysctl.proc_translated key and asserts the unified block.

Stacking

Opened stacked on matt/be-3399-hardware-block (#562) — hardware.py does not exist on main yet; it lands with #562. GitHub will retarget this PR to main when #562 merges; the diff here is just the net Rosetta change.

Testing

• pytest tests/comfy_cli/test_hardware.py → 20 passed
• ruff check + ruff format --check on the touched files → clean

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🔍 Cursor Review — Consolidated panel

Triggered by @mattmillerai.

✅ No high-signal findings.

Panel: 6/8 reviewers contributed findings.

Reviewers that did not contribute: kimi-k2.5:adversarial (empty), kimi-k2.5:edge-case (empty)