docs: clarify medical-use boundaries

[2023Anita]

Summary

• Add a top-level medical-use boundary callout to the README
• Clarify that vital-sign, fall-risk, apnea, distress, and triage outputs are experimental signals
• State that these outputs should not be used as the sole basis for diagnosis, treatment, alarm escalation, or continuous patient monitoring

Motivation

RuView's README introduces health-adjacent capabilities such as breathing rate, heart rate, fall risk, apnea screening, distress detection, and triage workflows very early. As a clinician/anesthesiologist reading the project, I think a short top-level boundary helps non-technical and clinical readers understand the intended use before trying the system in healthcare-adjacent scenarios.

This keeps the project positioning clear: research and ambient sensing first, not a regulated clinical monitoring device.

Verification

• git diff --check

Risk

Docs-only change. No runtime behavior, APIs, models, or examples are changed.