self-review 2026-05-29: fix dampening floor and cleanup route_create_node auto-link

Two changes:

1. el_runtime.c — engram_activation_dampen(): add floor of 0.35.
   ISE nodes with ac=900+ had dampen=0.128, giving effective salience=0.038
   which fell below the epist>=0.1 gate in engram_activate. This silently
   killed curiosity seeds "self identity values" and "decision pattern lesson"
   — the only corpus matches were high-ac ISEs that were then excluded from
   results, causing activated=0 on 50% of proactive_curiosity scans.
   Floor at 0.35 keeps salience=0.3 nodes at effective_bg=0.105, above the
   visibility threshold, without disrupting relative ordering of content nodes.

2. server.el — route_create_node: replace stale inline auto-link with
   auto_link_content_node(). The inline logic used the old engram_search_json
   (substring, no ISE filter) while the better BM25-based auto_link_content_node
   was added in 2026-05-28 and wired to /api/neuron/* routes but not to the
   raw /api/nodes POST path. Removes ~40 lines of duplicated logic.

lang/releases/v1.0.0-20260501/el_runtime.c

@@ -6603,9 +6603,22 @@ static double engram_temporal_decay(const EngramNode* n, int64_t now_ms) {
 
 /* Activation dampening: high activation_count nodes are "well-known" context
  * and get less marginal boost per firing.
- * count=0 → 1.0, count=2 → ~0.74, count=9 → ~0.59, count=99 → ~0.43 */
+ * count=0 → 1.0, count=2 → ~0.74, count=9 → ~0.59, count=99 → ~0.43
+ *
+ * FLOOR (2026-05-29 self-review): without a floor, ISE infrastructure nodes
+ * (salience=0.3, activation_count=900+) reach effective_salience=0.038, which
+ * falls below the epist>=0.1 visibility gate in engram_activate's result filter.
+ * This made entire curiosity seed sets permanently invisible — "self identity
+ * values" and "decision pattern lesson" reported activated=0 on every scan
+ * because the only corpus matches were high-ac ISE nodes that were then excluded.
+ *
+ * Fix: clamp dampen to a minimum of 0.35. At salience=0.3, this gives
+ * effective_bg = 0.105, which clears the 0.1 epist threshold. The floor is
+ * intentionally low enough that high-salience content nodes (0.5–0.8) still
+ * dominate — it only saves infrastructure nodes from total invisibility. */
 static double engram_activation_dampen(const EngramNode* n) {
-    return 1.0 / (1.0 + log(1.0 + (double)n->activation_count));
+    double d = 1.0 / (1.0 + log(1.0 + (double)n->activation_count));
+    return d < 0.35 ? 0.35 : d;
 }
 
 /* Temporal proximity bonus: boost propagation along edges connecting