Calibration qualification can accept an always-absent model without an occupied sensitivity control

A completed empty-room calibration can pass startup-baseline promotion while failing every known-occupied control. The promotion result therefore cannot establish occupancy qualification.

MEASURED on a Mac Catalyst app with its bundled arm64 sensing-server at dbf47886289b344fff8c399d5ff17c4cdf3b4da3 (PR #1936, based on #1903), four ESP32-C6 sources, 2026-09-16:

• Empty capture finalized with 19 baseline eigenvalues, active 256-subcarrier grid, no missing contributors.
• Learned residual threshold: 47.9984.
• Bootstrap promotion: 12/12 samples empty; baseline stored on disk.
• Subsequent operator-labelled phases: sitting 0/865 calibrated-present, walking 0/927, sitting 0/786. Raw heuristic reported presence; raw output is not ground truth.

The operator-labelled walking control falsifies sensitivity. A detector that always returns zero trivially satisfies an empty-only check. Disturbed-baseline threshold inflation is a plausible mechanism addressed separately by #1917; this issue concerns the missing qualification control regardless of the mechanism.

Important contract distinction: stored bootstrap models intentionally have negative-only authority. This is not a request to grant them positive presence or vitals authority. Keep bootstrap storage/background checks separate from a claim that the explicit field calibration is qualified for occupancy.

Suggested acceptance:

1. An always-absent model fails occupancy qualification against a known-occupied, operator-labelled held-out phase.
2. Pair sensitivity with a sufficiently long independent empty phase and report sample durations, false alarms and missed detections separately.
3. Match the exact boot/session/model/binding identity and require fresh CSI from the radio actually scored; refuse cached/stale evidence.
4. The Mac UI must distinguish stored bootstrap baseline from occupancy-qualified field calibration.
5. Include real app/server contract fixtures; schema literals and mocked frames alone do not establish producer/consumer compatibility.

Related: #1917, #1936, #1940. No production/fleet accuracy claim is made from this installation.