Adds engram_geo_displacement(A, B, core_frac) — a read-only interoceptive
primitive that measures how far a neighborhood descriptor B has drifted from a
baseline A and decomposes it into GROWTH (periphery extends, core fixed) vs
CORRUPTION (the invariant core displaces). The core is the top core_frac of A's
members by centrality; per shared member (matched by id) the displacement is the
change in radial position (dist_centroid). Centroid separation (L2 + cosine) and
radius delta give the aggregate move. Pure function, no store mutation, no flag.
HONESTLY PARTIAL: a live self-drift reading needs a persisted SelfAnchor
baseline to compare "now" against, and no persisted self node / anchored
self-neighborhood exists in this store yet. The primitive takes an EXPLICIT
baseline so it is real and testable today; capturing a durable SelfAnchor and
wiring the ENGRAM_DRIFT_SENSOR live reading is a flagged follow-up. We do not
fabricate a self silently.
MEASURED on synthetic descriptors:
- GROWTH (periphery 0.50->0.90, core fixed): core_disp=0.000, periph_disp=0.400,
centroid_sep=0.000, radius_delta=0.400.
- CORRUPTION (core 0.10->0.60, periphery fixed): core_disp=0.500,
periph_disp=0.000, centroid_sep=0.566.
- Identity A vs A: zero drift.
The sensor discriminates cleanly (corruption core_disp >> growth core_disp).
ASan+UBSan clean.
will.anderson
816b258255