identity: grant audit ledger — issue/refresh/revoke events, queryable per subject (10 tests)

audit.sx is an append-only ledger process. token.sx gains start/1(Audit)
and emits an event on every grant transition (issue, refresh, revoke —
including reuse-triggered revoke); start/0 stays unaudited so existing use
is unchanged (token.sx has no compile-time dep on the audit module, it just
sends to a pid). The ledger answers (identity/audit subject) via
audit/actions/count/all, chronological. In-memory event stream; persist
backing is a later Erlang<->persist bridge, out of scope. 111/111.

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

lib/identity/scoreboard.md

@@ -1,6 +1,6 @@
 # identity-on-sx Scoreboard
 
-**Total: 101 / 101 tests passing**
+**Total: 111 / 111 tests passing**
 
 |  | Suite | Pass | Total |
 |---|---|---|---|
@@ -12,6 +12,7 @@
 | ✅ | sso | 10 | 10 |
 | ✅ | membership | 17 | 17 |
 | ✅ | cache | 9 | 9 |
+| ✅ | audit | 10 | 10 |
 
 
 Generated by `lib/identity/conformance.sh`.