self-review 2026-08-02: bound the WM breakthrough storm; stop punishing semantic relevance for recency

Working memory was thrashing behind a healthy-looking gauge. wm_active sat
at 22-24 while breakthroughs ran 661-903 and evictions 485-717 PER 60s tick
- roughly 825-1125 nodes cycling in 5-call lockstep.

Root cause: the breakthrough path was an anti-starvation mechanism that reset
its own counter on firing, with no budget and no refractory. A node failing
its type threshold 5 times was force-promoted at exactly 0.10 and had its
suppression_count reset to 0, so it immediately restarted the identical
climb. Since BREAKTHROUGH_WEIGHT (0.10) > WM_FLOOR (0.05), every one of them
cleared the admission floor and entered the rank contest tied at 0.10, where
the tie-break degenerated to node-array index order. Cap-evicted nodes are
skipped by retrieval reinforcement, so they never got an access_ts record and
the STI inhibition-of-return damper never applied to them. That closed the
loop: re-suppressed, completely unmarked, forever.

An anti-starvation rule that resets its own counter without a bound is not a
fairness valve, it is an oscillator.

Fixes in engram_activate Pass 2:
- ENGRAM_BREAKTHROUGH_BUDGET (WM_CAP/4 = 6) caps intrusive thoughts per call.
- ENGRAM_BREAKTHROUGH_COOLDOWN (55) via NEGATIVE suppression_count. The field
  already serializes as %d and parses through eg_get_int_field, so negatives
  round-trip through snapshots with no struct or format change.
- Blocked breakthroughs no longer reset the counter; it saturates so a starved
  node surfaces on a later call instead of restarting from zero.
- Graded breakthrough weight by nearness to own threshold, so the rank
  tie-break is cognitive rather than insertion order. Invariant preserved:
  WM_FLOOR < weight < min(type_threshold).

Also: moved the additive cosine term AFTER the STI multiplier. It was applied
before, so an incumbent re-reached 30s later took t_n/(t_n+120) = 0.2x, which
cut the semantic term's ceiling from 0.20 to 0.04 - below every per-type
threshold. Meaning-match was being punished for having been recently useful.
Inhibition-of-return should rotate the structural score, not the semantic one.

Also: _eg_act_wm_evicted counted 3 of 5 eviction paths. The two carry-over
paths were silent, so the reported rate was an undercount of unknown
magnitude - while being used to diagnose an eviction pathology. All five now
increment.

Also: route_sync returned {"nodes":[],"edges":[]} when the snapshot export
failed. The soul's sync_ok check only tests for "" and "{}", so that
placeholder passed as a healthy sync: last_sync_ok_ts stamped, sync_age_ms
green, sync_empty never fired, added:0 forever. A broken sync was
indistinguishable from a quiet healthy one - the exact class this route was
added to fix. Returns a real error now.

Verified live (boot 20 vs boot 19): breakthroughs 661-903 -> 36/tick,
evictions 485-717 -> 12-46/tick against a counter that now covers more paths,
wm_active unchanged at 22-24, wm_avg_weight 0.138-0.273 -> 0.186-0.446.
Working memory is holding strong nodes instead of breakthrough-floor filler.

engram/src/server.el

@@ -311,7 +311,16 @@ fn route_sync(method: String, path: String, body: String) -> String {
     let snap_path: String = dir + "/.sync-export.json"
     engram_save(snap_path)
     let snap: String = fs_read(snap_path)
-    if str_eq(snap, "") { return "{\"nodes\":[],\"edges\":[]}" }
+    // 2026-08-02 self-review: this used to return {"nodes":[],"edges":[]} when
+    // the export/read failed. The soul's sync_ok test (awareness.el) only
+    // checks for "" and "{}", so that placeholder PASSED as a healthy sync:
+    // soul.last_sync_ok_ts got stamped, sync_age_ms stayed green, the
+    // sync_empty warn ISE never fired, and engram_sync reported added:0
+    // forever. A totally broken sync was indistinguishable from a quiet
+    // healthy one — the exact failure class this route was added to fix in
+    // the first place (see 2026-06-27 note above). Return a real error so the
+    // failure is loud on both sides.
+    if str_eq(snap, "") { return err_json("sync export failed: snapshot unreadable") }
     return snap
 }