mod: Ext 9 — policy dry-run trace diagnostics, 247/247

mod/trace-rules evaluates a report against every rule, returning each rule's
proved/unproved status + goal-by-goal derivation (an unproved rule shows which
goal failed). mod/first-proved = winner (matches engine precedence, cross-checked),
mod/proved-rules the firing set, mod/trace-report a [fires]/[ - ] rendering.
Answers 'why didn't my rule fire?' without instrumenting the engine. +15 tests.

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

lib/mod/conformance.conf

@@ -17,6 +17,7 @@ PRELOADS=(
   lib/mod/severity.sx
   lib/mod/offenders.sx
   lib/mod/quorum.sx
+  lib/mod/trace.sx
   lib/mod/lifecycle.sx
   lib/mod/audit.sx
   lib/mod/api.sx
@@ -36,4 +37,5 @@ SUITES=(
   "severity:lib/mod/tests/severity.sx:(mod-severity-tests-run!)"
   "offenders:lib/mod/tests/offenders.sx:(mod-offenders-tests-run!)"
   "quorum:lib/mod/tests/quorum.sx:(mod-quorum-tests-run!)"
+  "trace:lib/mod/tests/trace.sx:(mod-trace-tests-run!)"
 )