mod: Ext 2 — weighted/aggregate scoring (:score-at-least), 154/154

Report :signals ({:kind :weight}) project to signal(Id, 'kind', weight) facts;
condition (:score-at-least N) compiles to aggregate_all(sum(W), signal(Id,_,W),T),
T >= N. Low-confidence signals accumulate past a threshold via genuine Prolog
arithmetic aggregation. Default policy untouched — proven via custom rule sets.
+8 extension tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/mod/scoreboard.md

@@ -1,6 +1,6 @@
 # mod scoreboard
 
-**146 / 146 passing** (0 failure(s)).
+**154 / 154 passing** (0 failure(s)).
 
 | Suite | Passed | Total | Status |
 |-------|--------|-------|--------|
@@ -8,4 +8,4 @@
 | audit | 29 | 29 | ok |
 | escalation | 46 | 46 | ok |
 | fed | 26 | 26 | ok |
-| extensions | 14 | 14 | ok |
+| extensions | 22 | 22 | ok |