Issue #263: Default fall_thresh raised from 2.0 to 15.0 rad/s² — normal
walking produces accelerations of 2.5-5.0 which triggered constant false
"Fall Detected" alerts. Added consecutive-frame requirement (3 frames)
and 5-second cooldown debounce to prevent alert storms.
Issue #265: Added partitions_4mb.csv and sdkconfig.defaults.4mb for
ESP32-S3 boards with 4MB flash (e.g. SuperMini). OTA slots are 1.856MB
each, fitting the ~978KB firmware binary with room to spare.
Co-Authored-By: claude-flow <ruv@ruv.net>