artdag: Phase 7 optimisation laws as confluent maude module + 11 tests

lib/artdag/optimize-rules.sx — the effect-pipeline optimisation passes (identity
elim, no-op/zero-radius elim, adjacent fusion, idempotent over dedup) as a maude
module. Radius algebra is _+_ [assoc comm id: 0] (NOT Peano successor rules, which
are non-confluent here); mau/confluent? certifies 0 non-joinable critical pairs, so
the optimised pipeline's normal form / content id is rewrite-order stable. Consumes
lib/maude/confluence.sx. maude-optimize 25/25, total 183/183.

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

lib/artdag/conformance.sh

@@ -35,13 +35,15 @@ run_suite() {
 (load "lib/maude/matching.sx")
 (load "lib/maude/conditional.sx")
 (load "lib/maude/fire.sx")
+(load "lib/maude/confluence.sx")
 (load "lib/maude/rewrite.sx")
 (load "lib/maude/searchpath.sx")
 (load "lib/maude/strategy.sx")
 (load "lib/maude/meta.sx")
 (load "lib/maude/pretty.sx")
 (load "lib/maude/run.sx")'
-    BRIDGE_LOAD='(load "lib/artdag/maude-bridge.sx")'
+    BRIDGE_LOAD='(load "lib/artdag/maude-bridge.sx")
+(load "lib/artdag/optimize-rules.sx")'
   fi
   cat > "$TMP" << EPOCHS
 (epoch 1)