geometry: disagreement belongs on the edge, not averaged into the region

co_registration is corr(hebb strength, semantic proximity) over a region's
internal edges. Whether use and meaning agree is a property of EACH EDGE;
the correlation averages it into one scalar per region, so a region holding
one violently disagreeing edge beside one violently agreeing edge reports
~0. The disagreements cancel and the summary destroys exactly what it was
built to reveal — the mean-versus-min error, in different clothes.

Measured: 375 live neighborhoods, 340 positive, 31 AT ZERO, 4 negative.
Read as a count that says 'four things to be curious about'. Read correctly
it says four were lopsided enough to survive averaging, and the 31 zeros
are where opposing sites cancelled.

The loop computing the aggregate already had both halves per edge — w and
cs — and threw them away. Now:
    discord = z(semantic proximity) - z(association strength)
standardized within the region from accumulators already gathered. No
second statistic, no constant, no threshold; |discord| IS the nucleation
strength. >0 near in meaning yet unlinked by use; <0 linked by use yet far
in meaning. Both surprising.

This also removes the reason curiosity looked like a search problem. With a
per-region number the only way to find sites is to enumerate regions — I
wrote exactly that sweep, and it is a supervisor walking the structure,
O(n) per call, fine at 375 and impossible at a million. Nothing in a mind
scans its neighborhoods to find what is surprising; the surprise captures
attention. That sweep is reverted here.

co_registration is deprecated, not deleted: it is embedded in the persisted
GEO1 blob and removing it is a format migration that must not ride along.
Nothing new may read it.

lang/runtime/el_runtime.h

@@ -666,6 +666,12 @@ el_val_t  engram_get_node(el_val_t id);
 void      engram_strengthen(el_val_t node_id);
 void      engram_forget(el_val_t node_id);
 el_val_t  engram_prune_telemetry(el_val_t older_than_ms);
+/* Register the ambient-consolidation step and start dreaming. Resolved by
+ * dlsym, like http_set_handler. The handler performs ONE step and returns
+ * non-zero if it did work; returning zero parks the dreamer until engagement
+ * changes. There is no schedule and must never be one. */
+void      dream_set_handler(el_val_t name);
+
 el_val_t  engram_node_count(void);
 /* Attach a Geometry to an existing node, and read the attached width back.
  * Named for the operation, not the store: a node acquires geometry. This is