self-review 2026-08-04: restore working-memory continuity; learn graph structure from co-activation

WM continuity (the significant one). A node reached by the current query but
scoring under its type threshold was zeroed outright, while a node the query
did NOT reach got the full ACT-R carry-over treatment. Being found was punished
relative to not being found. Measured consequence: WM turned over 100% every
call — three activations of a byte-identical query gave |A∩B| = |B∩C| = 0 — and
wm_evicted stayed 0 the whole time because that path never counted. WM was not
a working set; it was six suppression-breakthrough nodes re-drawn per call.
Both exits from a WM slot now share one extracted retention rule.
Result: WM 6 -> 24 nodes (the designed Cowan capacity), top weight 0.097 ->
0.748 (natural promotion, not the breakthrough floor), and contents that are
actually query-relevant.

Hebbian learning. Edge weights were written once at engram_connect and never
changed; last_fired's only writer in 12.5k lines was an unrelated dharma path.
Every learning mechanism operated on nodes — the wiring between them was
frozen. Adds co-activation potentiation (HeLa-Mem arXiv:2604.16839) in a
separate `hebb` field so authored structure is never mutated, with homeostatic
per-node scaling the source lacks (PNAS 2422602122) to prevent hub saturation.

Measuring it produced the finding that mattered: zero edges existed between
co-active WM members, so reweighting existing edges was a no-op. This graph's
41k edges were all authored by explicit tool calls — nothing had ever formed an
association from experience. So Hebb literally: if the wire is absent, grow it.
Consolidation is gated hard (sustained EWMA past 0.15, <=2/call, 5% ceiling,
in-memory candidates discarded on restart) because it permanently mutates the
graph.

Two bugs caught only by instrumenting rather than assuming: the snap-to-zero
floor sat above the per-step increment, so nothing could ever accumulate; and
the reached-but-sub-threshold eviction above. Verified live end to end — 53
links formed under load, then discarded with the test snapshot.

Also exposes engram_act_stats_json over GET /api/act-stats. It had existed
since 2026-07-27 but was reachable only through the soul daemon, so diagnosing
the activation layer required a working soul. This review needed it and could
not get at it.

engram/src/server.el

@@ -76,6 +76,20 @@ fn route_stats(method: String, path: String, body: String) -> String {
     engram_stats_json()
 }
 
+// route_act_stats — GET /api/act-stats
+// (2026-08-04 self-review) engram_act_stats_json() has existed since the
+// 2026-07-27 review but was reachable ONLY through the soul daemon's heartbeat
+// binding. Every activation-layer gauge — WM evictions, breakthroughs, embedder
+// breaker state, context drift, and now the Hebbian counters — was therefore
+// invisible unless the soul happened to be running and its ISEs were read back
+// out of the store. Diagnosing the activation layer required a working soul,
+// which is exactly backwards: the lower layer should be observable on its own.
+// This review needed it to verify link formation and could not get at it. One
+// line of plumbing, and the whole activation layer becomes directly diagnosable.
+fn route_act_stats(method: String, path: String, body: String) -> String {
+    engram_act_stats_json()
+}
+
 // (2026-07-18 self-review) Scoping sweep: `let` inside an if-block creates an
 // inner scope only — it does NOT mutate the outer binding (documented with
 // evidence in awareness.el, 2026-05-25). Every default/reassignment below used
@@ -507,6 +521,9 @@ fn handle_request(method: String, path: String, body: String) -> String {
     if str_eq(method, "GET") && (str_eq(clean, "/api/stats") || str_eq(clean, "/stats")) {
         return route_stats(method, path, body)
     }
+    if str_eq(method, "GET") && (str_eq(clean, "/api/act-stats") || str_eq(clean, "/act-stats")) {
+        return route_act_stats(method, path, body)
+    }
 
     // Nodes
     if str_eq(method, "POST") && (str_eq(clean, "/api/nodes") || str_eq(clean, "/nodes")) {