feat: exchange scoped approval service tokens per request

Assistant: codex
Assistant-Model: gpt-5.6-luna
Assistant-Session: 01a07ff8-19d0-7820-b4d0-1353833cb7fc

docs/evidence/2026-09-09-approval-identity-exercise.json

@@ -0,0 +1,34 @@
+{
+  "schema_version": 1,
+  "target": "disposable local processes; synthetic credentials",
+  "started_at": "2026-09-09T01:49:09.187005+00:00",
+  "keycape_image": "forgejo.coulomb.social/coulomb/key-cape@sha256:7ff54c54e63ee172ae9e6e7fd2da96e427352f712343d74626ee6fe0f6f82611",
+  "approval_engine_commit": "b46b0f26669dc83c944ee5145426bad03d5ef720",
+  "keycape_contract_commit": "0f5535eed95f1223c83a28f5a0bd6fa594cecae8",
+  "consumer_source_sha256": {
+    "approval_auth.py": "6f3b033e7928e1c527bc19f5a1e01bf243540769a8646bd8cd47268da25637b5",
+    "approval_consume.py": "cd79b3e4534a5abf55af2b5ab2939c485a3140a1174f593e0aa7719250051d92",
+    "config.py": "2f2f1b60664d89bbb806aed0c768378923062077740e1f96e4c359238eb06955",
+    "service_auth.py": "653723ef5babce2157771416d93cb15cdbb7caca3c45509c3730520c55e4515c"
+  },
+  "limitations": [
+    "PDP sequencing double",
+    "local Approval Engine source, not deployed image",
+    "no live custody or client-side read grant",
+    "no OpenBao effect or model execution"
+  ],
+  "checks": {
+    "operator_issued_and_approved_via_verified_jwt": true,
+    "wrong_action_refused_before_consume": true,
+    "actual_consumer_claim_check_consume": true,
+    "same_digest_retry_idempotent": true,
+    "different_digest_refused": true,
+    "spent_claim_refused": true,
+    "operator_consume_scope_denied_by_issuer": true,
+    "wrong_secret_refused": true,
+    "no_access_token_file_created": true
+  },
+  "status": "passed",
+  "cleanup_complete": true,
+  "finished_at": "2026-09-09T01:49:11.402008+00:00"
+}