Harden the PEP harness and KeyCape registration request

Close remaining in-repo APPROVAL-WP-0002 gaps: drive GH-DEC-2026-003 against
the real HTTP surface, fail closed on JWT/human-consume/static-token paths,
treat audit 200 duplicates as drained, and ask KeyCape for the production
audience and client grants.

Assistant: grok
Assistant-Session: 01a06253-e557-7971-93d9-4f4c2cfbf455

tests/test_audit.py

@@ -45,6 +45,41 @@ def test_audit_sender_adapts_envelope_and_rereads_token(tmp_path):
     engine.close()
 
 
+def test_duplicate_audit_status_marks_drained(tmp_path):
+    token = tmp_path / "token"
+    token.write_text("token")
+    engine = Engine(":memory:", clock=lambda: FROZEN)
+    approve(engine)
+    sink = AuditCoreSink(
+        "http://audit-core:8080", token, opener=lambda *_args, **_kwargs: Response(200)
+    )
+    result = engine.drain(sink)
+    assert result == {"delivered": 1, "failed": 0}
+    assert engine.undrained() == []
+    engine.close()
+
+
+def test_httperror_audit_status_remains_pending(tmp_path):
+    from io import BytesIO
+    from urllib.error import HTTPError
+
+    token = tmp_path / "token"
+    token.write_text("token")
+    engine = Engine(":memory:", clock=lambda: FROZEN)
+    approve(engine)
+
+    def opener(request, timeout):
+        raise HTTPError(
+            request.full_url, 503, "unavailable", hdrs=None, fp=BytesIO(b"no")
+        )
+
+    sink = AuditCoreSink("http://audit-core:8080", token, opener=opener)
+    result = engine.drain(sink)
+    assert result == {"delivered": 0, "failed": 1}
+    assert engine.undrained()[0]["last_error"] == "AuditDeliveryError"
+    engine.close()
+
+
 def test_nonaccepted_audit_status_remains_pending(tmp_path):
     token = tmp_path / "token"
     token.write_text("token")