self-review 2026-08-03: gate curiosity auto-terms on label document frequency

Reject an extracted auto-term when its label document frequency exceeds
node_count/400 (floor 8) -- measured live at 12,859 nodes, threshold 32.

Live label df separates the classes by an order of magnitude:
  rejected: <!--:220  SELF:175  Engram:125  CORE:88  STAR:36
  passed:   Dual:12  Sparse:8  Latent:6  MemQ:1  dGRPO:1  engram_goal_bias:1

Verified against the running soul (boot 21). Peak curiosity activation fell
from 541 to 113; the flood terms (SELF, CORE, Engram, STAR, <!--) are absent
from post-fix scans while topical compound identifiers pass untouched.
Sample is 7 scans -- suggestive, not conclusive; watch the next review.

Nested conditional rather than max(): El let is single-assignment, so the
floor is expressed as a second conjunct.

Verification note: content df was tested as an alternative signal and
rejected -- 'Curiosity' has the highest content df in the store (5526) yet
one of the lowest activation counts (113). Label df is the correct field
because label is what the first-word extractor reads.

dist/awareness.c

@@ -289,6 +289,13 @@ el_val_t auto_term_try_slot(el_val_t slot_type, el_val_t slot_lbl) {
         if (str_contains(term, EL_STR("'"))) {
           state_set(EL_STR("_ats_gw"), EL_STR("1"));
         }
+        el_val_t df_max = (engram_node_count() / 400);
+        el_val_t df_term = engram_label_df(term);
+        if (df_term > df_max) {
+          if (df_term > 8) {
+            state_set(EL_STR("_ats_gw"), EL_STR("1"));
+          }
+        }
         if (str_eq(term, state_get(EL_STR("soul.tabu_t0")))) {
           state_set(EL_STR("_ats_gw"), EL_STR("1"));
         }