mod: Phase 2 — evidence accumulation + proof trees + audit log, 60/60

Reports carry an :evidence list, asserted as evidence/3 facts; reviewer-remove
rule (highest precedence) lets human review override classification. Proof tree
built constructively by re-querying each rule body goal against the same DB with
the report id bound, so derivations carry real unification bindings. Append-only
audit log records decision + proof + evidence snapshot per decide, monotonic seq,
never mutates prior entries. +29 audit tests.

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

lib/mod/scoreboard.json

@@ -1,10 +1,11 @@
 {
   "lang": "mod",
-  "total_passed": 31,
+  "total_passed": 60,
   "total_failed": 0,
-  "total": 31,
+  "total": 60,
   "suites": [
-    {"name":"decide","passed":31,"failed":0,"total":31}
+    {"name":"decide","passed":31,"failed":0,"total":31},
+    {"name":"audit","passed":29,"failed":0,"total":29}
   ],
-  "generated": "2026-06-06T17:30:06+00:00"
+  "generated": "2026-06-06T17:36:32+00:00"
 }