docs: complete MM-Fi WiFi-sensing study (pose + action, the honest picture)

Consolidates the full campaign into one committed, citable artifact (the
detailed log was in a gitignored staging report): pose SOTA 83.6% + 20KB
int4 edge model; action recognition 88% (a WiFi task MM-Fi never
benchmarked); the generalization story (zero-shot collapse, few-shot
calibration rescue, task-general across pose+action); all honest negatives
(CORAL/DANN/instance-norm/SupCon/distillation/subject-scaling); the 11KB
calibration-adapter deployment recipe; honest limitations (cross-dataset
untested, ARM latency pending).

Co-Authored-By: claude-flow <ruv@ruv.net>