NotchAgent pi integration fork

Based on ykushch/notchagent (https://github.com/ykushch/notchagent),
licensed under the Apache License, Version 2.0. The upstream LICENSE is retained.

Changes in this fork include pi harness parent/child discovery, root-only
attention with a 30-second blocked grace period, explicit needs-human metadata
and escalated-question decoding, read-only notchctl tree diagnostics, a distinct
bundle identifier (co.schoolintel.notch-pi), and disabled upstream update checks.