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/tests/audit.sx

@@ -0,0 +1,109 @@
+;; identity/tests/audit.sx — the grant audit ledger. Every grant
+;; transition is recorded; the ledger is queryable per subject and
+;; chronological. Covers issue/refresh/revoke wiring through the token
+;; registry, reuse-triggered revoke, per-subject isolation, and direct
+;; ledger use.
+
+(define id-audit-test-count 0)
+(define id-audit-test-pass 0)
+(define id-audit-test-fails (list))
+
+(define
+  id-audit-test
+  (fn
+    (name actual expected)
+    (set! id-audit-test-count (+ id-audit-test-count 1))
+    (if
+      (= actual expected)
+      (set! id-audit-test-pass (+ id-audit-test-pass 1))
+      (append! id-audit-test-fails {:name name :expected expected :actual actual}))))
+
+(define ida-ev erlang-eval-ast)
+(define idanm (fn (v) (get v :name)))
+
+(identity-load-audit!)
+(identity-load-token!)
+
+;; ── issue is audited ─────────────────────────────────────────────
+
+(id-audit-test
+  "issue records one event for the subject"
+  (ida-ev
+    "A = identity_audit:start(),\n     Reg = identity_tokens:start(A),\n     identity_tokens:issue(Reg, alice, web, read),\n     identity_audit:count(A, alice)")
+  1)
+
+(id-audit-test
+  "the recorded action is issue"
+  (idanm
+    (ida-ev
+      "A = identity_audit:start(),\n       Reg = identity_tokens:start(A),\n       identity_tokens:issue(Reg, alice, web, read),\n       case identity_audit:actions(A, alice) of\n         [issue] -> matched;\n         _ -> nomatch\n       end"))
+  "matched")
+
+;; ── full grant lifecycle is audited in order ─────────────────────
+
+(id-audit-test
+  "issue, refresh, revoke are recorded in order"
+  (idanm
+    (ida-ev
+      "A = identity_audit:start(),\n       Reg = identity_tokens:start(A),\n       {ok, G, R} = identity_tokens:issue_grant(Reg, alice, web, read),\n       identity_tokens:refresh(Reg, R),\n       identity_tokens:revoke(Reg, G),\n       case identity_audit:actions(A, alice) of\n         [issue, refresh, revoke] -> matched;\n         _ -> nomatch\n       end"))
+  "matched")
+
+;; ── reuse-triggered revoke is audited ────────────────────────────
+
+(id-audit-test
+  "a refresh-reuse cascade records a revoke event"
+  (idanm
+    (ida-ev
+      "A = identity_audit:start(),\n       Reg = identity_tokens:start(A),\n       {ok, _G, R} = identity_tokens:issue_grant(Reg, alice, web, read),\n       identity_tokens:refresh(Reg, R),\n       identity_tokens:refresh(Reg, R),\n       case identity_audit:actions(A, alice) of\n         [issue, refresh, revoke] -> matched;\n         _ -> nomatch\n       end"))
+  "matched")
+
+;; ── per-subject isolation ────────────────────────────────────────
+
+(id-audit-test
+  "the ledger separates subjects"
+  (ida-ev
+    "A = identity_audit:start(),\n     Reg = identity_tokens:start(A),\n     identity_tokens:issue(Reg, alice, web, read),\n     identity_tokens:issue(Reg, bob, cli, write),\n     identity_tokens:issue(Reg, alice, mobile, read),\n     identity_audit:count(A, alice)")
+  2)
+
+(id-audit-test
+  "an unaudited subject has zero events"
+  (ida-ev
+    "A = identity_audit:start(),\n     Reg = identity_tokens:start(A),\n     identity_tokens:issue(Reg, alice, web, read),\n     identity_audit:count(A, ghost)")
+  0)
+
+;; ── the full log accumulates across subjects ─────────────────────
+
+(id-audit-test
+  "all events accumulate in the ledger"
+  (ida-ev
+    "A = identity_audit:start(),\n     Reg = identity_tokens:start(A),\n     identity_tokens:issue(Reg, alice, web, read),\n     identity_tokens:issue(Reg, bob, cli, write),\n     length(identity_audit:all(A))")
+  2)
+
+;; ── start/0 stays unaudited (no regression) ──────────────────────
+
+(id-audit-test
+  "an unaudited registry still issues working tokens"
+  (idanm
+    (ida-ev
+      "Reg = identity_tokens:start(),\n       {ok, T} = identity_tokens:issue(Reg, alice, web, read),\n       case identity_tokens:introspect(Reg, T) of\n         {active, _, _, _} -> active;\n         {inactive} -> inactive\n       end"))
+  "active")
+
+;; ── direct ledger use (e.g. login/consent events) ────────────────
+
+(id-audit-test
+  "events can be recorded directly on the ledger"
+  (idanm
+    (ida-ev
+      "A = identity_audit:start(),\n       identity_audit:record(A, alice, login),\n       identity_audit:record(A, alice, consent),\n       case identity_audit:actions(A, alice) of\n         [login, consent] -> matched;\n         _ -> nomatch\n       end"))
+  "matched")
+
+(id-audit-test
+  "an audit entry carries its subject"
+  (idanm
+    (ida-ev
+      "A = identity_audit:start(),\n       identity_audit:record(A, alice, login),\n       case identity_audit:audit(A, alice) of\n         [{_, Subject, _}] -> Subject;\n         _ -> nomatch\n       end"))
+  "alice")
+
+(define
+  id-audit-test-summary
+  (str "audit " id-audit-test-pass "/" id-audit-test-count))