test(relay): cross-package e2e adversarial security harness

New e2e/ package wires the REAL P5(auth)+P4(crypto)+P2(agent) exports through
in-memory seams and an untrusted-relay attacker vantage (RelaySpy). Dynamically
re-validates F1–F4/F6 plus MITM/reflection/replay/reorder/INV2/cross-tenant/
single-use — every assertion runs the production code path. 21 tests green, tsc
clean. node_modules via symlinks (gitignored); no npm install needed.

e2e/package.json

@@ -0,0 +1,12 @@
+{
+  "name": "relay-e2e-suite",
+  "version": "0.0.0",
+  "private": true,
+  "type": "module",
+  "description": "Cross-package end-to-end + adversarial security test harness for the rendezvous-relay service. Wires the REAL P1/P2/P4/P5/P6 exports through in-memory seams and an untrusted-relay attacker vantage; dynamically re-validates the audit findings F1-F6 plus MITM/replay/reflect/INV2/cross-tenant.",
+  "scripts": {
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "typecheck": "tsc --noEmit"
+  }
+}