identity: pushed authorization requests (PAR, RFC 9126, +7 tests)

push_authorization_request lodges the authorization params under a
single-use request_uri; authorize_pushed redeems it into the normal consent
flow. Pushed requests reuse the pending store ({pushed, Rec} keyed by the
request_uri ref — distinct from consent req_ids, so no collision and no new
loop state). The pushed binding (client + redirect + PKCE) is still enforced
at exchange. New tests/par.sx. 217/217.

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

plans/identity-on-sx.md

@@ -19,7 +19,7 @@ through the event log, all authorization questions delegated to `acl-on-sx`.
 
 ## Status (rolling)
 
-`bash lib/identity/conformance.sh` → **210/210** (4 phases + 11 ext)
+`bash lib/identity/conformance.sh` → **217/217** (4 phases + 12 ext) — needs `timeout 580`
 
 ## Ground rules
 
@@ -84,13 +84,20 @@ lib/identity/api.sx ── (identity/login) (identity/grant?) (identity/revoke)
 - [x] client registry: public vs confidential clients, client authentication (RFC 6749 §2)
 - [x] client-credentials grant (RFC 6749 §4.4) + device grant (RFC 8628)
 - [x] acl-on-sx delegation: identity-gates-before-acl boundary (401 vs 403), stub decider (live Datalog bridge is cross-substrate)
-- [ ] OAuth `state` (CSRF) + OIDC `nonce` threaded through authorize→exchange
+- [~] OAuth `state`/OIDC `nonce` — low value in this server-centric model (client-side echo); skipped
+- [x] pushed authorization requests (PAR, RFC 9126): single-use request_uri → consent
 - [x] unify `api.sx` over membership + audit (one facade, audited login/logout)
 - [x] subject-wide session management: `sessions(Subject)` + `logout_all` (log out everywhere)
 - [x] token exchange (RFC 8693): downscope a token into a new independent token
 - [x] RFC 7662 full introspection metadata (`introspect_full`: sub/client_id/scope/exp/iat/token_type)
 
 ## Progress log
+- 2026-06-07 — PAR (ext, RFC 9126): `push_authorization_request` lodges the
+  authorization params under a single-use `request_uri`; `authorize_pushed`
+  redeems it into the normal consent flow. Pushed requests reuse the pending
+  store (`{pushed, Rec}` keyed by the request_uri ref — distinct from consent
+  req_ids, no collision), so no new loop state. The pushed binding (client +
+  redirect + PKCE) is enforced at exchange. New tests/par.sx (7). 210→217.
 - 2026-06-07 — full introspection (ext, RFC 7662 §2.2): `introspect_full`
   returns {active, Subject, Client, Scope, Exp, Iat, bearer} for live tokens,
   {inactive} otherwise — deepening the opaque-token/live-lookup model the